Highly durable carbon-based catalyst for fuel cells, method for producing the same, and polymer electrolyte fuel cell including the same

Abstract

This paper describes a highly durable carbon-based catalyst for fuel cells, which is coated with a highly corrosion-resistant ceramic material to protect the carbon-based support, which is subject to rapid corrosion in the operating environment of the fuel cell, and a method for producing the same, as well as a polymer electrolyte fuel cell including the same.

Description

[Technical Field]

[0001] The present invention relates to a highly durable carbon-based catalyst for fuel cells, a manufacturing method thereof, and a polymer electrolyte fuel cell including the same. More specifically, the present invention relates to a highly durable carbon-based catalyst for fuel cells, in which a highly corrosion-resistant ceramic material is coated to form a ceramic coating layer with needle-like protrusions in order to protect the carbon-based support, which is subject to rapid corrosion in the operating environment of the fuel cell, a manufacturing method thereof, and a polymer electrolyte fuel cell including the same.

[0002] The information on the national research and development project of the present invention is as follows: [Project unique number]1711120511 [Project Number] 2020M3H4A3105824 [Department name] Ministry of Science, ICT and Communication [Name of issue management (specialized) organization] Korea Research Foundation [Research Project Name] Materials Innovation Leading Project [Research title] Development of core technology for the basic materials of ultra-high durability carbon-based supports [Contribution rate] 1 / 1 [Name of project execution organization] Korea Ceramic Technology Institute [Research period] August 24, 2020 - December 31, 2024 [Background technology]

[0003] Fuel cells are devices that generate electricity by converting chemical energy into electrical energy through the oxidation of hydrogen fuel. Fuel cells can use hydrogen produced using renewable energy, and produce water as a reaction product. They are attracting attention as an environmentally friendly energy source because they do not produce air pollutants or greenhouse gases.

[0004] These fuel cells are classified into Proton Exchange Membrane Fuel Cells (PEMFC), Direct Methanol Fuel Cells (DMFC), Phosphoric Acid Fuel Cells (PAFC), Molten Carbonate Fuel Cells (MCFC), and Solid Oxide Fuel Cells (SOFC), depending on the type of electrolyte and fuel used.

[0005] Among these, polymer electrolyte fuel cells have a relatively low operating temperature, high energy density, and excellent fast start-up and response characteristics, and are therefore the subject of active technological research for use as an energy source in automobiles, various electronic devices, transportation, and power generation.

[0006] In a fuel cell, hydrogen is supplied to the anode and oxygen is supplied to the cathode, and the catalyst in the anode oxidizes the hydrogen to form protons. The protons then pass through the proton conducting membrane and undergo a reduction reaction with oxygen by the catalyst in the cathode, producing electricity.

[0007] A fuel cell includes an anode, a cathode, and an electrolyte membrane disposed between the anode and the cathode, each of which includes a catalyst including an active support and a carbon-based support supporting the active support.

[0008] Hydrogen injected into the anode of the fuel cell is separated into hydrogen ions and electrons, and air is injected into the cathode of the fuel cell, where oxygen ions and electrons are separated. Electricity is generated by the movement of the separated electrons, and water (H2O) is produced when hydrogen and oxygen come into contact, generating heat.

[0009] Meanwhile, FIG. 1 is a schematic diagram for explaining a conventional fuel cell catalyst, and a more specific explanation will be given with reference to this.

[0010] As shown in Figure 1, conventional fuel cells use catalysts to improve reaction efficiency. Conventional fuel cell catalysts use platinum (Pt), which has excellent oxygen reduction reaction properties, and a carbon-based support to support the platinum (Pt).

[0011] However, conventional fuel cell catalysts undergo an oxidation reaction of the carbon support (C + 2H2O → CO2 + 4H++4e - ), which causes desorption and aggregation of platinum (Pt), resulting in a phenomenon in which the performance of the catalyst is reduced.

[0012] Furthermore, in the operating environment of a fuel cell, the carbon-based support rapidly oxidizes and corrodes, resulting in a rapid decrease in the performance of the electrode.

[0013] A related prior art document is Korean Patent Publication No. 10-0708732 (published on April 17, 2007), which describes an anode for a fuel cell, a method for manufacturing the same, and a fuel cell equipped with the same. Summary of the Invention [Problem to be solved by the invention]

[0014] The present invention aims to provide a highly durable carbon-based catalyst for fuel cells, which is coated with a highly corrosion-resistant ceramic material to form a ceramic coating layer with needle-like protrusions in order to protect the carbon-based support, which is subject to rapid corrosion in the operating environment of the fuel cell; a method for manufacturing the same; and a polymer electrolyte fuel cell including the same. [Means for solving the problem]

[0015] In order to achieve the above object, an embodiment of the present invention provides a carbon-based catalyst for a fuel cell having excellent durability, which includes a carbon-based support, a ceramic coating layer covering the surface of the carbon-based support, and an active support supported on the ceramic coating layer covering the carbon-based support, and the ceramic coating layer is formed so that a portion of the ceramic coating layer protrudes in a needle-like shape from the surface of the carbon-based support.

[0016] The carbon-based support includes at least one selected from the group consisting of carbon nanotubes, graphene, and activated carbon.

[0017] The ceramic coating layer is made of one or more materials selected from the group consisting of TiO2, Al2O3, ZrO2, and CeO2.

[0018] The ceramic coating layer has a thickness of 10 nm to 10 μm.

[0019] The ceramic coating layer has a surface portion that covers the surface of the carbon-based support, and a plurality of protrusions that are arranged spaced apart from one another from the surface portion, protrude outward from the surface portion, and have a needle-like shape in part.

[0020] The active support includes at least one selected from platinum (Pt), ruthenium (Ru), palladium (Pd), rhodium (Rh), iridium (Ir), osmium (Os), and gold (Au).

[0021] In order to achieve the above object, according to an embodiment of the present invention, there is provided a polymer electrolyte fuel cell including a carbon-based catalyst for a fuel cell having excellent durability, comprising: a cathode; an anode disposed at a distance from the cathode; an electrolyte membrane disposed between the cathode and the anode; gas diffusion layers disposed on the outer sides of the cathode and the anode, respectively; and separators disposed on the outer sides of the gas diffusion layers, respectively; wherein at least one of the cathode and the anode comprises a carbon-based support; a ceramic coating layer covering the surface of the carbon-based support; and a carbon-based catalyst having an active support supported on the ceramic coating layer covering the carbon-based support, wherein the ceramic coating layer is formed so that a portion thereof protrudes in a needle-like shape from the surface of the carbon-based support.

[0022] The ceramic coating layer is made of one or more materials selected from the group consisting of TiO2, Al2O3, ZrO2, and CeO2.

[0023] The ceramic coating layer has a thickness of 10 nm to 10 μm.

[0024] The ceramic coating layer has a surface portion that covers the surface of the carbon-based support, and a plurality of protrusions that are arranged spaced apart from one another from the surface portion, protrude outward from the surface portion, and have a needle-like shape in part.

[0025] In order to achieve the above object, an embodiment of the present invention provides a method for manufacturing a durable carbon-based catalyst for a fuel cell, which includes the steps of: (a) acid-treating a carbon-based support; (b) forming a ceramic coating layer on the surface of the acid-treated carbon-based support; and (c) supporting an active support on the ceramic coating layer covering the surface of the carbon-based support, wherein in step (b), the ceramic coating layer is formed so that a portion thereof protrudes in a needle-like shape from the surface of the carbon-based support.

[0026] The step (a) includes: (a-1) mixing the carbon-based support with an acidic solution and stirring at a speed of 500 to 1,500 rpm to perform an acid treatment; and (a-2) filtering and washing the acid-treated carbon-based support.

[0027] In the step (a-1), the acid treatment is carried out at a temperature of 100 to 140° C. for 1 to 10 hours.

[0028] The step (b) includes the steps of: (b-1) adding the acid-treated carbon-based support to a solvent and then mixing by ultrasonic treatment; (b-2) mixing a ceramic precursor and a curing agent into the ultrasonic-treated suspension and stirring to perform hydrothermal synthesis; and (b-3) filtering, washing, and drying the result of the hydrothermal synthesis to form a ceramic coating layer covering the surface of the carbon-based support.

[0029] In the step (b-2), the hydrothermal synthesis is carried out at 160 to 240° C. for 10 to 30 hours.

[0030] In the step (b-3), the ceramic coating layer is made of one or more materials selected from the group consisting of TiO2, Al2O3, ZrO2, and CeO2.

[0031] The step (c) includes the steps of: (c-1) immersing the ceramic coating layer covering the surface of the carbon-based support in an active support precursor solution, and then adding a strong base solution to perform hydrothermal synthesis; and (c-2) filtering, washing, and drying the result of the hydrothermal synthesis to support an active support on the ceramic coating layer covering the surface of the carbon-based support.

[0032] In the step (c-1), the hydrothermal synthesis is carried out at 100 to 200° C. for 1 to 6 hours.

[0033] In the step (c-2), the active support comprises at least one selected from platinum (Pt), ruthenium (Ru), palladium (Pd), rhodium (Rh), iridium (Ir), osmium (Os), and gold (Au). [Effects of the Invention]

[0034] The highly durable carbon-based catalyst for fuel cells and the polymer electrolyte fuel cell including the same according to the present invention have a ceramic coating layer formed on the surface of a carbon-based support, and an active support is supported on the ceramic coating layer covering the surface of the carbon-based support, thereby improving corrosion resistance and preventing the carbon-based support from being oxidized and corroded in the operating environment of the fuel cell, thereby improving electrode performance.

[0035] Furthermore, the highly durable carbon-based catalyst for fuel cells and the polymer electrolyte fuel cell including the same according to the present invention have the effect of reducing the D-band vacancy of the active support (Pt) through electron transfer from the carbon-based support and the ceramic coating layer, and improving the stabilization of the catalyst through strong metal-support interaction (SMSI).

[0036] In addition, the carbon-based catalyst for a fuel cell having excellent durability according to the present invention and the polymer electrolyte fuel cell including the same have a ceramic coating layer formed in a needle shape with a portion protruding outward from the surface of the carbon-based support, which not only improves the specific surface area but also reduces the amount of OH. - This makes it possible to suppress the adsorption of radicals such as H2O2 and improve durability. [Brief explanation of the drawings]

[0037] [Figure 1] FIG. 1 is a schematic diagram illustrating a conventional fuel cell catalyst. [Figure 2] 1 is a schematic diagram illustrating a polymer electrolyte fuel cell including a carbon-based catalyst for a fuel cell having excellent durability according to an embodiment of the present invention. [Figure 3] 1 is a cross-sectional view showing a carbon-based catalyst for a fuel cell having excellent durability according to an embodiment of the present invention. [Figure 4] 1 is a schematic diagram illustrating the operating principle of a carbon-based catalyst for a fuel cell having excellent durability according to an embodiment of the present invention. [Figure 5] 1 is a schematic diagram illustrating the operating principle of a carbon-based catalyst for a fuel cell having excellent durability according to an embodiment of the present invention. [Figure 6] 1A to 1C are schematic process diagrams illustrating a method for producing a carbon-based catalyst for a fuel cell with excellent durability according to an embodiment of the present invention. [Figure 7] 1A to 1C are schematic process diagrams illustrating a method for producing a carbon-based catalyst for a fuel cell with excellent durability according to an embodiment of the present invention. [Figure 8] 1A to 1C are schematic process diagrams illustrating a method for producing a carbon-based catalyst for a fuel cell with excellent durability according to an embodiment of the present invention. [Figure 9] 1 is a graph showing the results of XRD measurement for catalysts according to Examples 1 and 2 and Comparative Example 1. [Figure 10] 1 is a photograph showing catalysts according to Examples 1 and 2. [Figure 11] 1 is a graph showing the results of evaluating the physical properties of half cells manufactured using catalysts according to Examples 1 and 2 and Comparative Example 1. [Figure 12] 1 is a graph showing the results of evaluating the physical properties of half cells manufactured using catalysts according to Examples 1 and 2 and Comparative Example 1. [Figure 13] 1 is a graph showing the results of evaluating the physical properties of half cells manufactured using catalysts according to Examples 1 and 2 and Comparative Example 1. [Figure 14] 1 is a graph showing the results of evaluating the physical properties of fuel cells manufactured using catalysts according to Examples 1 and 2 and Comparative Examples 1 and 2. [Figure 15] 1 is a graph showing the results of evaluating the physical properties of fuel cells manufactured using catalysts according to Examples 1 and 2 and Comparative Examples 1 and 2. DETAILED DESCRIPTION OF THE INVENTION

[0038] The advantages and features of the present invention, as well as methods for achieving them, will become clearer with reference to the following detailed examples in conjunction with the accompanying drawings. However, the present invention is not limited to the examples disclosed below, and may be embodied in various different forms. However, these examples are provided to complete the disclosure of the present invention and to fully convey the scope of the invention to those skilled in the art to which the present invention pertains, and the present invention is defined only by the scope of the claims. The same reference symbols throughout the specification refer to the same components.

[0039] Hereinafter, a carbon-based catalyst for a fuel cell having excellent durability, a method for manufacturing the same, and a polymer electrolyte fuel cell including the same according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0040] FIG. 2 is a schematic diagram showing a polymer electrolyte fuel cell including a carbon-based catalyst for a fuel cell having excellent durability according to an embodiment of the present invention, and FIG. 3 is a cross-sectional view showing a carbon-based catalyst for a fuel cell having excellent durability according to an embodiment of the present invention.

[0041] 2 and 3, a polymer electrolyte fuel cell 100 including a carbon-based catalyst for a fuel cell with excellent durability according to an embodiment of the present invention includes a cathode 110, an anode 120 disposed spaced apart from the cathode 110, and an electrolyte membrane 130 disposed between the cathode 110 and the anode 120. The cathode 110, the anode 120, and the electrolyte membrane 130 constitute a membrane-electrode assembly (MEA) 150.

[0042] In addition, the polymer electrolyte fuel cell 100 including the carbon-based catalyst for a fuel cell having excellent durability according to an embodiment of the present invention may further include gas diffusion layers 162 and 164 arranged on the outside of the cathode 110 and the anode 120, respectively, and separators 172 and 171 arranged on the outside of the gas diffusion layers 162 and 164, respectively.

[0043] Here, the gas diffusion layers 162, 164 may include a first gas diffusion layer 162 disposed on the outside of the cathode 110 and a second gas diffusion layer 164 disposed on the outside of the anode 120. Furthermore, the separator plates 172, 174 may include a first separator plate 172 disposed on the outside of the first gas diffusion layer 162 and a second separator plate 174 disposed on the outside of the second gas diffusion layer 164.

[0044] In this case, at least one of the cathode 110 and the anode 120 includes a carbon-based catalyst 50 having a carbon-based support 10, a ceramic coating layer 20 covering the surface of the carbon-based support 10, and an active support 30 supported on the ceramic coating layer 20 covering the carbon-based support 10.

[0045] As described above, the carbon-based catalyst 50 for a fuel cell having excellent durability according to the embodiment of the present invention includes the carbon-based support 10 , the ceramic coating layer 20 , and the active carrier 30 .

[0046] The carbon-based support 10 serves as a support for supporting the active carrier 30. The carbon-based support 10 includes one or more selected from carbon nanotubes, graphene, and activated carbon, among which carbon nanotubes are more preferably used.

[0047] The ceramic coating layer 20 is formed to cover the surface of the carbon-based support 10. The ceramic coating layer 20 is intended to protect the carbon-based support 10, which is subject to rapid corrosion in the operating environment of the fuel cell, and is preferably formed of a highly corrosion-resistant ceramic material. For this reason, the ceramic coating layer 20 is preferably formed of one or more materials selected from TiO2, Al2O3, ZrO2, and CeO2, and more preferably formed of TiO2.

[0048] The ceramic coating layer 20 is formed so that parts thereof protrude in a needle-like shape from the surface of the carbon-based support 10. More specifically, the ceramic coating layer 20 has a surface portion 22 that covers the surface of the carbon-based support 10, and a plurality of protrusions 24 that are arranged spaced apart from one another from the surface portion 22, protrude outward from the surface portion 22, and have some parts formed in a needle-like shape.

[0049] In this way, the protrusions 24 of the ceramic coating layer 20 are arranged so that multiple protrusions are spaced apart from each other and protrude outward from the surface of the carbon-based support 110, which has the structural advantage of greatly expanding the specific surface area.

[0050] Therefore, in the carbon-based catalyst 100 for fuel cells having excellent durability according to an embodiment of the present invention, the protrusions 24 of the ceramic coating layer 20 are formed so as to protrude outward from the surface of the carbon-based support 10, which not only makes it possible to ensure a high specific surface area but also makes it possible to suppress the adsorption of radicals such as OH and H2O2, thereby improving durability.

[0051] These ceramic coating layers 20 have a thickness of 10 nm to 10 μm. death, A more preferred range is a thickness of 100 nm to 1 μm. If the thickness of the ceramic coating layer 20 is less than 10 nm, the thickness is too thin and the effect of improving corrosion resistance may not be fully exhibited. Conversely, if the thickness of the ceramic coating layer 20 exceeds 10 μm, an excessively thick design may reduce electrical conductivity, which is undesirable.

[0052] The active support 30 is supported on a ceramic coating layer 20 that covers the carbon-based support 10. Here, a precious metal having excellent oxygen reduction reaction properties is used for the active support 30. More specifically, the active support 30 can be made of one or more metals selected from platinum (Pt), ruthenium (Ru), palladium (Pd), rhodium (Rh), iridium (Ir), osmium (Os), and gold (Au), and among these, it is more preferable to use platinum (Pt).

[0053] Meanwhile, FIGS. 4 and 5 are schematic diagrams illustrating the operating principle of a carbon-based catalyst for a fuel cell having excellent durability according to an embodiment of the present invention.

[0054] As shown in FIGS. 4 and 5, the highly durable carbon-based catalyst 50 for a fuel cell according to an embodiment of the present invention is formed by coating the surface of a carbon-based support with a highly corrosion-resistant ceramic material to form a ceramic coating layer 20 with needle-like protrusions in order to protect the carbon-based support from rapid corrosion in the operating environment of the fuel cell.

[0055] Furthermore, the highly durable carbon-based catalyst 50 for fuel cells according to the embodiment of the present invention has the effect of reducing the D-band vacancy of the active support 30 (Pt) through electron transfer from the carbon-based support and the ceramic coating layer 20, and improving the stabilization of the catalyst through strong metal-support interaction (SMSI).

[0056] Furthermore, the carbon-based catalyst 50 for fuel cells, which has excellent durability according to an embodiment of the present invention, has a ceramic coating layer 20 formed in a needle shape with a portion protruding outward from the surface of the carbon-based support, which not only improves the specific surface area but also suppresses the adsorption of radicals such as OH and H2O2, thereby improving durability.

[0057] The carbon-based catalyst for a fuel cell having excellent durability according to the above-described embodiments of the present invention and the polymer electrolyte fuel cell including the same have a ceramic coating layer formed on the surface of the carbon-based support, and an active support is supported on the ceramic coating layer covering the surface of the carbon-based support, thereby improving corrosion resistance and preventing the carbon-based support from being oxidized and corroded in the operating environment of the fuel cell, thereby improving electrode performance.

[0058] Furthermore, the highly durable carbon-based catalyst for fuel cells according to the embodiments of the present invention and the polymer electrolyte fuel cell including the same have the effect of reducing the D-band vacancy of the active support (Pt) through electron transfer from the carbon-based support and the ceramic coating layer, and improving the stabilization of the catalyst through strong metal-support interaction (SMSI).

[0059] In addition, the carbon-based catalyst for a fuel cell having excellent durability according to the embodiment of the present invention and the polymer electrolyte fuel cell including the same have a ceramic coating layer formed in a needle shape with a portion protruding outward from the surface of the carbon-based support, which not only improves the specific surface area but also prevents OH - This makes it possible to suppress the adsorption of radicals such as H2O2 and improve durability.

[0060] Hereinafter, a method for manufacturing a carbon-based catalyst for a fuel cell having excellent durability according to an embodiment of the present invention will be described with reference to the accompanying drawings.

[0061] 6 to 8 are process diagrams illustrating a method for producing a carbon-based catalyst for a fuel cell having excellent durability according to an embodiment of the present invention.

[0062] As shown in Fig. 6, the carbon-based support 10 is subjected to an acid treatment. This acid treatment includes a process of mixing the carbon-based support 10 with an acidic solution and stirring at a speed of 500 to 1,500 rpm, and a process of filtering and washing the acid-treated carbon-based support 10.

[0063] In this case, it is preferable that the acid treatment be carried out using an acidic aqueous solution containing one or more acids selected from sulfuric acid, nitric acid, and hydrochloric acid having a pH of 2 or less. This is because, although using an acidic aqueous solution having a pH higher than 2 is advantageous in terms of modifying the surface of the carbon-based support 10, it may cause environmental pollution.

[0064] These acid treatments are preferably carried out at a temperature of 100 to 140°C for 1 to 10 hours. If the acid treatment temperature is less than 100°C or the acid treatment time is less than 1 hour, the acid treatment is insufficient, and the effect of improving the specific surface area is not fully achieved. Conversely, if the acid treatment temperature exceeds 140°C or the acid treatment time exceeds 10 hours, no further improvement in the effect is achieved and this may only increase the production cost, which is uneconomical.

[0065] Next, as shown in FIG. 7, a ceramic coating layer 20 is formed on the surface of the acid-treated carbon-based support 10.

[0066] The steps for forming these ceramic coating layers include the steps of adding the acid-treated carbon-based support 10 to a solvent and then mixing it with ultrasonic treatment, mixing the ultrasonically treated suspension with a ceramic precursor and a curing agent and stirring to perform hydrothermal synthesis, and filtering and washing the result of the hydrothermal synthesis and drying it to form the ceramic coating layer 20 that covers the surface of the carbon-based support 10.

[0067] Here, the ultrasonic treatment is preferably carried out for 30 to 180 minutes under conditions of a frequency of 25 to 35 kHz and an output voltage of 5 to 10 W. If the ultrasonic output voltage is less than 5 W or the ultrasonic treatment time is less than 30 minutes, the effect of improving dispersibility may not be fully achieved. Conversely, if the ultrasonic output voltage exceeds 10 W or the ultrasonic treatment time exceeds 180 minutes, excessive application of ultrasonic waves may cause damage to the acid-treated carbon-based support, which is not preferred.

[0068] Furthermore, the hydrothermal synthesis is preferably carried out at 160 to 240°C for 10 to 30 hours. If the hydrothermal synthesis temperature is less than 160°C or the hydrothermal synthesis time is less than 10 hours, the hydrothermal synthesis may not be carried out sufficiently, and the ceramic coating layer 20 may not be completely coated on the surface of the carbon-based support 10. Conversely, if the hydrothermal synthesis temperature exceeds 240°C or the hydrothermal synthesis time exceeds 30 hours, there is a risk that no further improvement in the effect will be achieved and only an increase in production costs and time will occur, which is undesirable from an economical standpoint.

[0069] Here, washing is preferably carried out at least twice using distilled water, and drying can be carried out at 60 to 80°C for 10 to 20 hours, but is not limited thereto.

[0070] In this case, the ceramic coating layer 20 is preferably formed of one or more materials selected from TiO2, Al2O3, ZrO2, and CeO2, and more preferably TiO2. In this manner, the surface of the carbon-based support 10 is coated with a ceramic material having excellent corrosion resistance, and then dried to form the ceramic coating layer 20, thereby improving the corrosion resistance of the catalyst.

[0071] These ceramic coating layers 20 are formed so that parts thereof protrude in a needle-like shape from the surface of the carbon-based support 10. More specifically, the ceramic coating layer 20 has a surface portion that covers the surface of the carbon-based support 10, and a plurality of protrusions that are arranged spaced apart from one another from the surface portion, protrude outward from the surface portion, and have some of the protrusions formed in a needle-like shape.

[0072] In this way, the protrusions of the ceramic coating layer 20 are arranged so that multiple protrusions are spaced apart from each other and protrude outward from the surface of the carbon-based support 10, which has the structural advantage of greatly expanding the specific surface area.

[0073] Therefore, the carbon-based catalyst for fuel cells, which is highly durable and manufactured by the method according to the embodiment of the present invention, is formed so that the protrusions of the ceramic coating layer 20 protrude outward from the surface of the carbon-based support 10, which not only ensures a high specific surface area but also suppresses the adsorption of radicals such as OH and H2O2, thereby improving durability.

[0074] The ceramic coating layer 20 preferably has a thickness of 10 nm to 10 μm, and more preferably a thickness of 100 nm to 1 μm. If the thickness of the ceramic coating layer 20 is less than 10 nm, the thickness is too thin and the effect of improving corrosion resistance may not be fully exhibited. Conversely, if the thickness of the ceramic coating layer 20 exceeds 10 μm, an excessive thickness design may reduce electrical conductivity, which is undesirable.

[0075] Next, as shown in FIG. 8, an active support 30 is supported on the ceramic coating layer 20 covering the surface of the carbon-based support 10 .

[0076] In this case, the supporting step includes a process of immersing the ceramic coating layer 20 covering the surface of the carbon-based support 10 in an active support precursor solution, adding a strong base solution to perform hydrothermal synthesis, and a process of filtering, washing, and drying the result of the hydrothermal synthesis to support the active support 30 on the ceramic coating layer 20 covering the surface of the carbon-based support 10.

[0077] The strong base solution can be a 0.5 to 1.5 M aqueous sodium hydroxide solution.

[0078] Here, the hydrothermal synthesis is preferably carried out at 100 to 200°C for 1 to 6 hours. If the hydrothermal synthesis temperature is less than 100°C or the hydrothermal synthesis time is less than 1 hour, the active support 30 may not be uniformly supported on the ceramic coating layer 20 covering the surface of the carbon-based support 10. Conversely, if the hydrothermal synthesis temperature exceeds 200°C or the hydrothermal synthesis time exceeds 6 hours, no further improvement in the effect is achieved and this may only increase the production cost, which is uneconomical.

[0079] Here, a precious metal having excellent oxygen reduction reaction properties is used for the active support 30. More specifically, the active support 30 can be made of one or more selected from platinum (Pt), ruthenium (Ru), palladium (Pd), rhodium (Rh), iridium (Ir), osmium (Os), and gold (Au), and among these, it is more preferable to use platinum (Pt).

[0080] As described above, the method for producing a carbon-based catalyst for a fuel cell having excellent durability according to the embodiment of the present invention is completed.

[0081] Example The structure and operation of the present invention will be described in more detail below with reference to preferred embodiments of the present invention, which are presented as preferred examples of the present invention and are not to be construed as limiting the present invention in any sense.

[0082] The contents not described here will not be explained here because they can be fully inferred by those skilled in the art.

[0083] 1. Manufacturing of carbon-based catalysts for fuel cells Example 1 1 g of multi-walled carbon nanotubes (MWCNTs) was mixed with 130 ml of aqueous sulfuric acid solution and 70 ml of aqueous nitric acid solution, and the mixture was stirred at 120° C. for 4 hours at a speed of 1,000 rpm for acid treatment, and then filtered and washed.

[0084] Next, 0.1 g of acid-treated multi-walled carbon nanotubes (MWCNTs) was added to 50 mL of IPA, and then ultrasonically treated and mixed for 1 hour under conditions of a frequency of 20 KHz and an output voltage of 8 W.

[0085] Next, 0.3 mL of titanium tetraisopropoxide (TTIP) and 0.26 mL of diethylenetriamine (DETA) were added to the ultrasonically treated suspension, and the mixture was stirred at 1,500 rpm for 30 minutes and subjected to hydrothermal synthesis at 200°C for 12 hours.

[0086] Next, the result of the hydrothermal synthesis was filtered and washed, and then dried at 70°C for 12 hours to produce a TiO2 coating layer covering the surface of the multi-walled carbon nanotubes (MWCNTs).

[0087] Next, the TiO2 coating layer covering the surface of multi-walled carbon nanotubes (MWCNTs) was immersed in H2PtCl6·6H2O, and then an aqueous NaOH solution was added and hydrothermal synthesis was carried out at a temperature of 160°C for 2 hours.

[0088] Next, the hydrothermally synthesized product was filtered and washed, and then dried at 70°C for 12 hours to support Pt on the TiO2 coating layer covering the surface of multi-walled carbon nanotubes (MWCNTs), producing a carbon-based catalyst (TiO2-CNT@30Pt) for fuel cells.

[0089] Example 2 A carbon-based catalyst (TiO-CNT@30Pt) for fuel cells was prepared in the same manner as in Example 1, except that the TiO coating layer covering the surface of multi-walled carbon nanotubes (MWCNTs) was prepared by hydrothermal synthesis at 200°C for 24 hours.

[0090] Comparative Example 1 1 g of multi-walled carbon nanotubes (MWCNTs) was mixed with 130 ml of aqueous sulfuric acid solution and 70 ml of aqueous nitric acid solution, and the mixture was stirred at 120° C. for 4 hours at a speed of 1,000 rpm for acid treatment, and then filtered and washed.

[0091] Next, 0.1 g of acid-treated multi-walled carbon nanotubes (MWCNTs) was added to 50 mL of IPA, and then ultrasonically treated and mixed for 1 hour under conditions of a frequency of 20 KHz and an output voltage of 8 W.

[0092] Next, multi-walled carbon nanotubes (MWCNTs) were immersed in H2PtCl6·6H2O, and then NaOH aqueous solution was added and hydrothermal synthesis was carried out at a temperature of 160 °C for 2 h.

[0093] Next, the result of the hydrothermal synthesis was filtered and washed, and then dried at 70°C for 12 hours to support Pt on multi-walled carbon nanotubes (MWCNTs) and prepare a carbon-based catalyst (CNT@30Pt) for fuel cells.

[0094] Comparative Example 2 A commercial catalyst (40 wt% Pt / C) from Premetek was obtained.

[0095] 2. Observation of microstructure Fig. 9 is a graph showing the XRD measurement results for the catalysts according to Examples 1 and 2 and Comparative Example 1, and Fig. 10 is a photograph showing the catalysts according to Examples 1 and 2. In this regard, Fig. 10(a) and (b) are SEM and TEM photographs showing the catalyst according to Example 1, and Fig. 10(c) and (d) are SEM and TEM photographs showing the catalyst according to Example 2.

[0096] 9, it can be seen that the catalysts according to Examples 1 and 2 have Pt, C, and TiO2(anatase) peaks detected because the CNT surface is coated with TiO2 and Pt is supported. On the other hand, the catalyst according to Comparative Example 1 does not have the CNT surface coated with TiO2, and therefore no TiO2(anatase) peak is detected.

[0097] As shown in FIG. 10, it can be seen that the catalysts according to Examples 1 and 2 have a TiO2 coating layer formed on the surface of the CNT, with some of the layers protruding outward in needle-like shapes.

[0098] 3. Evaluation of physical properties Table 1 shows the results of evaluating the physical properties of the half-cells manufactured using the catalysts according to Examples 1 and 2 and Comparative Example 1. Also, FIGS. 11 to 13 are graphs showing the results of evaluating the physical properties of the half-cells manufactured using the catalysts according to Examples 1 and 2 and Comparative Example 1.

[0099] [Table 1]

[0100] As shown in Table 1 and FIGS. 11 to 13, the physical property test results for the half-cells according to Examples 1 and 2 and the half-cell according to Comparative Example 1 are shown.

[0101] The electrolyte used was a 0.1 M perchloric acid solution, which was fully saturated with nitrogen before measurement. The electrochemical active surface area (ECSA), which indicates the number of exposed active sites per unit weight, was measured. Comparative Example 1 and Example 1 showed similar values, but Example 2, which had a thick ceramic coating layer, showed a lower value due to insufficient electrical conductivity caused by the insulating properties of the ceramic coating layer and clumping within the catalyst.

[0102] The onset potential and half-wave potential, which indicate the catalytic reaction rate, were highest in Example 1. This is due to the increased number of needle-like active sites within the catalyst, which increased the reaction rate between oxygen gas and platinum. This can also be evidenced by the Tafel slope. The Tafel slope, which is another indicator of electrochemical reaction rate relative to overpotential, indicates that the more active the reaction within the catalyst, the more active the reaction. The lower slope in Example 1 compared to Comparative Example 1 indicates the more active the internal reaction within the catalyst. While Example 1 showed the highest mass activity, which indicates activity per unit area of ​​platinum, its specific activity was approximately 0.1 V lower than Comparative Example 1. This is thought to be due to the lack of electrical conductivity and particle agglomeration caused by the insulating properties of the ceramic coating layer, as indicated by the ECSA value. As can be seen from the limit current density (limit current) at which the concentration of reactants in the catalyst layer converges to 0, Comparative Example 1 shows a higher value than Example 1. This means that the more excellent the electrical conductivity of a sample, the higher the value shown, and therefore the ceramic coating layer is located inside the catalyst of Example 1, causing an insulating phenomenon.

[0103] Meanwhile, Table 2 summarizes the assembly and test conditions for fuel cells manufactured using the catalysts according to Examples 1 and 2 and Comparative Examples 1 and 2, and Table 3 shows the results of evaluating the physical properties of fuel cells manufactured using the catalysts according to Examples 1 and 2 and Comparative Examples 1 and 2. Also, Figures 14 and 15 are graphs showing the results of evaluating the physical properties of fuel cells manufactured using the catalysts according to Examples 1 and 2 and Comparative Examples 1 and 2.

[0104] [Table 2]

[0105] [Table 3]

[0106] As shown in Tables 2 and 3, and FIGS. 14 and 15, the results of physical property tests on the fuel cells according to Examples 1 and 2 and the fuel cells according to Comparative Examples 1 and 2 are shown.

[0107] For performance experiments and durability tests in the actual operating environment of the fuel cell, a membrane electrode assembly (MEA) of a polymer electrolyte fuel cell was fabricated. The components and test conditions used are shown in Table 2.

[0108] The electrolyte used in this experiment was Nafion212 (Dupont), and the fuel electrode was a commercial gas diffusion electrode (GDE) coated with 0.5 mg of platinum per area. The air electrode was a gas diffusion layer (GDL) coated with 0.2 mg of platinum catalyst per area using a hand spray method, and a membrane electrode assembly (MEA) was completed by applying heat and pressure at nearly 130°C. The electrode area of ​​both the hot electrode and the air electrode was 0.5 cm. 2 was identical to

[0109] The flow rates of the fuel electrode and air electrode of the membrane electrode assembly were set at 105 mL / min of hydrogen gas and 330 mL / min of oxygen gas, respectively, and after sufficient humidification at 70° C., an IV curve was obtained.

[0110] To evaluate the long-term durability of fuel cell catalysts, the accelerated stability test (AST) protocol for polymer electrolyte fuel cell membrane electrode assemblies (MEAs) published by the US Department of Energy (DOE) was used. Tests were rapidly repeated at a rate of 500mV / s within the potential range of 1.0-1.5V, where carbon oxidation occurs rapidly. After 5,000 cycles, the electrochemically active area (ECSA) of the catalyst and the change in maximum power density (MPD) on the IV curve were measured to examine the degree of catalyst degradation.

[0111] As shown in FIG. 14 and Table 3, Comparative Examples 1 and 2 exhibited superior initial performance compared to Examples 1 and 2. When comparing the open circuit voltage (OCV), which refers to the resistance of a circuit when no voltage is applied, Examples 1 and 2 exhibited a higher OCV. This is because the ceramic coating layer, which acts as an insulator, also functions as a resistor. Consequently, the maximum power density (MPD) also differed. Example 2, which had the thickest ceramic coating layer, exhibited the lowest MPD, while Comparative Example 2, which had the smallest catalyst particle size and the best platinum particle dispersion, exhibited the highest MPD. However, the electrochemically active surface area degradation (ECSA) after 5,000 cycles was superior in Examples 1 and 2, indicating that the ceramic coating layer on the surface of the carbon-based support maintained the cell performance of the membrane electrode assembly (MEA) even after rigorous durability testing.

[0112] This indicates that the ceramic coating layer inside the catalyst not only successfully prevents the carbon-based support from oxidizing and corroding, but also exerts a strong metal-support interaction (SMSI) effect, reducing the D-band vacancy of the active support (Pt) through electron transfer from the carbon-based support and the ceramic coating layer.

[0113] In addition, as shown in FIG. 15, the deterioration rate of not only the electrochemically active surface area (ECSA) of the cathode but also the maximum power density (MPD), which indicates the overall cell performance, is 6 to 8 times lower than that of Comparative Examples 1 and 2. This is because the OH - This means that the adsorption of radicals such as H2O2 is reduced, improving not only degradation at the cathode but also the overall durability of the cell.

[0114] Although the present invention has been described above with reference to its preferred embodiments, various modifications and variations may be made by those skilled in the art. These modifications and variations are within the scope of the present invention as long as they do not deviate from the scope of the technical concept provided by the present invention. Therefore, the scope of the present invention should be determined by the following claims. [Explanation of symbols]

[0115] 100 Polymer electrolyte fuel cell 110 cathode 120 anodes 130 Electrolyte Membrane 150 Membrane electrode assembly 162 First gas diffusion layer 164 Second gas diffusion layer 172 1st separation plate 174 Second separation plate

Claims

1. a carbon-based support; a ceramic coating layer covering the surface of the carbon-based support; an active carrier supported on a ceramic coating layer covering the carbon-based support; Including, The ceramic coating layer has a thickness of 10 nm to 10 μm and is formed so that a part of the ceramic coating layer protrudes in a needle-like shape from the surface of the carbon-based support. A highly durable carbon-based catalyst for fuel cells.

2. The carbon-based support is The material contains at least one selected from carbon nanotubes, graphene, and activated carbon. The carbon-based catalyst for fuel cells according to claim 1, which has excellent durability.

3. The ceramic coating layer is TiO ２ , Al ２ O ３ , ZrO ２ , and CeO ２ It is characterized in that it is formed of one or more materials selected from the following: The carbon-based catalyst for fuel cells according to claim 1, which has excellent durability.

4. The ceramic coating layer is a surface portion covering the surface of the carbon-based support; a plurality of protrusions arranged at intervals from the surface portion, protruding outward from the surface portion, and having a needle-like shape; characterized in that it has The carbon-based catalyst for fuel cells according to claim 1, which has excellent durability.

5. The active support is The present invention is characterized in that it contains one or more elements selected from the group consisting of platinum (Pt), ruthenium (Ru), palladium (Pd), rhodium (Rh), iridium (Ir), osmium (Os), and gold (Au). The carbon-based catalyst for fuel cells according to claim 1, which has excellent durability.

6. a cathode; an anode disposed spaced apart from the cathode; an electrolyte membrane disposed between the cathode and the anode; gas diffusion layers disposed on the outer sides of the cathode and anode, respectively; Separation plates respectively disposed on the outer sides of the gas diffusion layers; Including, At least one of the cathode and the anode is The carbon-based catalyst includes a carbon-based support, a ceramic coating layer covering the surface of the carbon-based support, and an active support supported on the ceramic coating layer covering the carbon-based support, The ceramic coating layer has a thickness of 10 nm to 10 μm and is formed so that a part of the ceramic coating layer protrudes in a needle-like shape from the surface of the carbon-based support. A polymer electrolyte fuel cell containing a carbon-based catalyst for a highly durable fuel cell.

7. The ceramic coating layer is TiO ２ , Al ２ O ３ , ZrO ２ , and CeO ２ It is characterized in that it is formed of one or more materials selected from the following: A polymer electrolyte fuel containing the carbon-based catalyst for a fuel cell according to claim 6, which has excellent durability. battery.

8. The ceramic coating layer is a surface portion covering the surface of the carbon-based support; a plurality of protrusions arranged at intervals from the surface portion, protruding outward from the surface portion, and having a needle-like shape; characterized in that it has A polymer electrolyte fuel containing the carbon-based catalyst for a fuel cell according to claim 6, which has excellent durability. battery.

9. (a) acid treating a carbon-based support; (b) forming a ceramic coating layer on the surface of the acid-treated carbon-based support; (c) supporting an active support on a ceramic coating layer covering the surface of the carbon-based support; Including, In step (b), the ceramic coating layer has a thickness of 10 nm to 10 μm and is formed so that a part of the ceramic coating layer protrudes from the surface of the carbon-based support in a needle-like shape. A method for manufacturing durable carbon-based catalysts for fuel cells.

10. The above step (a) (a-1) mixing the carbon-based support with an acidic solution and stirring at a speed of 500 to 1,500 rpm to perform an acid treatment; (a-2) filtering and washing the acid-treated carbon-based support; characterized in that it comprises The method for producing the carbon-based catalyst for fuel cells having excellent durability according to claim 9.

11. In the above step (a-1), The acid treatment is characterized in that it is carried out at a temperature of 100 to 140 ° C. for 1 to 10 hours; The method for producing the carbon-based catalyst for fuel cells having excellent durability according to claim 10.

12. The above step (b) (b-1) adding the acid-treated carbon-based support to a solvent and then mixing by ultrasonic treatment; (b-2) mixing the ultrasonically treated suspension with a ceramic precursor and a curing agent, stirring, and performing hydrothermal synthesis; (b-3) filtering, washing, and drying the result of the hydrothermal synthesis to form a ceramic coating layer covering the surface of the carbon-based support; characterized in that it comprises The method for producing the carbon-based catalyst for fuel cells having excellent durability according to claim 9.

13. In the above step (b-2), The hydrothermal synthesis is Carrying out the reaction at 160 to 240 ° C for 10 to 30 hours, The method for producing the carbon-based catalyst for fuel cells having excellent durability according to claim 12.

14. In the above step (b-3), The ceramic coating layer is TiO ２ , Al ２ O ３ , ZrO ２ , and CeO ２ The material is made of one or more materials selected from the following: The method for producing the carbon-based catalyst for fuel cells having excellent durability according to claim 12.

15. The above step (c) (c-1) immersing the ceramic coating layer covering the surface of the carbon-based support in an active support precursor solution, and then adding a strong base solution to perform hydrothermal synthesis; (c-2) filtering, washing, and drying the result of the hydrothermal synthesis, and supporting an active support on the ceramic coating layer covering the surface of the carbon-based support; characterized in that it comprises The method for producing the carbon-based catalyst for fuel cells having excellent durability according to claim 9.

16. In the above step (c-1), The hydrothermal synthesis is Carrying out the reaction at 100 to 200°C for 1 to 6 hours, The method for producing the carbon-based catalyst for fuel cells having excellent durability according to claim 15.

17. In the above step (c-2), The active support is Platinum (Pt), ruthenium (Ru), palladium (Pd), rhodium (Rh), iridium containing at least one selected from the group consisting of irradiated tungsten (Ir), osmium (Os), and gold (Au). characterized in that The method for producing the carbon-based catalyst for fuel cells having excellent durability according to claim 15.

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