Method for producing fuel cell catalyst

Abstract

A method of manufacturing a fuel cell catalyst may include a method of manufacturing a carbon support for a fuel cell catalyst, wherein the carbon support has improved catalytic metal binding force and improved carbon durability. The carbon support may be coated with a carbon layer that is highly doped with heteroatoms. The carbon layer may be formed by uniformly compounding a conductive polymer containing heteroatoms with a carbon support and thermally treating the compounded mixture.

Description

Technical Field

[0001] The present disclosure relates to a method for producing a catalyst for a fuel cell. Background Art

[0002] In proton exchange membrane fuel cells (PEMFCs), the electrode catalyst layer consists of a carbon support loaded with platinum (Pt) and an ionomer used as a binder. Platinum and alloy catalysts used as fuel cell catalysts are configured to load platinum or alloy particles onto a carbon support, which plays the most important role in battery performance and durability, and the performance of the catalyst is greatly affected by the structure and properties of the catalytic particles and the carbon support. Therefore, it is extremely urgent and important to develop optimized catalysts to ensure the performance and durability of hydrogen electric vehicles.

[0003] In fuel cell catalysts, carbon supports act as electron conductors to transfer electrons to catalytic particles and as supports to disperse catalytic nanoparticles to enhance catalytic activity. Therefore, the physical properties required of carbon supports are: (1) high conductivity to improve electron transfer efficiency; (2) high porosity to evenly distribute catalysts of a few nanometers and reduce mass transfer resistance in high current density areas; (3) high durability to resist carbon corrosion that may occur during fuel cell operation; and (4) carbon surface properties to improve catalyst dispersion and catalyst-support bonding.

[0004] Specifically, the durability of the carbon carrier can be improved by increasing the graphitization degree and the thickness of the carbonized layer on the carbon surface. Generally speaking, the improvement of the graphitization degree is limited because it can only be improved by high-temperature heat treatment above 2000°C, and the surface of the carbon material with a graphitized structure has a high hydrophobicity, so when the catalyst particles are loaded, the bonding strength between the carrier and the catalyst particles is weak.

[0005] In addition, in order to solve the problem of platinum dissolution and reduced durability of Pt catalysts during fuel cell operation, it is very important to control the surface of the carbon support to improve the interface attraction between the catalytic particles and the carbon support. To this end, various methods have been investigated and studied, such as: methods of doping the surface of the carbon support with heteroatoms such as B, N, S and P; carbon surface treatments such as plasma and ozone treatments; and the introduction of nano-metal particles. However, the technical level is still low. Summary of the invention

[0006] In order to develop the next generation of carbon supports that simultaneously satisfy durability and improved performance, a new synthesis strategy that can strike a balance between the desired properties is needed. The present disclosure relates to a method for manufacturing a catalyst for a fuel cell, and in particular provides a carbon support having improved bonding with a catalytic metal and improved carbon durability, wherein the carbon support is coated with a carbon layer highly doped with heteroatoms, and the carbon layer is formed by uniformly compounding a conductive polymer containing heteroatoms with the carbon support and heat-treating the resulting mixture.

[0007] Some embodiments of the present disclosure can solve the problems in the prior art and provide a method for improving the bonding force between the catalytic metal and the carbon support by forming a carbonized layer on the surface of the carbon material from a precursor polymer containing heteroatoms. Specifically, some embodiments of the present disclosure aim to achieve improved durability against platinum dissolution and ensure the durability of the carbon support.

[0008] The advantages of the present disclosure are not necessarily limited to the above advantages. The above and other advantages of the present disclosure will become more apparent from the following description, and can be achieved through the embodiments described in the various combinations of the claims and embodiments.

[0009] According to an embodiment of the present disclosure, a method for manufacturing a fuel cell catalyst may include: synthesizing a precursor polymer; preparing a carrier dispersion comprising a precursor polymer and a carbon material; preparing an intermediate having a structure in which a surface of a carbon material is coated with the precursor polymer; fixing the precursor polymer on the surface of the carbon material by performing a primary heat treatment on the intermediate; converting the precursor polymer into a carbonized layer by performing a secondary heat treatment on the intermediate to prepare a carbon carrier; and introducing a catalytic metal into the carbonized layer to produce a catalyst. The carbonized layer may contain at least one heteroatom selected from sulfur (S), nitrogen (N), phosphorus (P) and combinations thereof.

[0010] In one embodiment, the precursor polymer may include a conductive polymer.

[0011] In one embodiment, the synthesis of the precursor polymer may include introducing a polymer raw material and an initiator into a first organic solvent to prepare a precursor dispersion, and may include a process in which the polymer raw material is dissolved in the precursor dispersion to cause an initiation reaction and a polymerization reaction.

[0012] The polymerization reaction may include a process of stirring the precursor dispersion, and the stirring may be performed at a temperature ranging from 0° C. to 80° C. for 3 to 48 hours.

[0013] In one embodiment, the method may further include washing and drying after the stirring.

[0014] In one embodiment, the polymer raw material may include at least one selected from the group consisting of nitrogen-containing organic materials, sulfur-containing organic materials, nitrogen-containing and sulfur-containing organic materials, phosphorus-containing organic materials, and polymers thereof.

[0015] Specifically, the nitrogen-containing organic material may include at least one selected from pyrrole, guanine, adenine, purine, melamine, urea, pyridine, aniline, dicyandiamide, ethylenediamine, ethylenediaminetetraacetic acid (EDTA), and combinations thereof.

[0016] The sulfur-containing organic material may include at least one selected from the group consisting of dibenzyl disulfide, thiophene, 2,2-dithiophene, p-toluenesulfonic acid, 2-thiophene methanol, and combinations thereof.

[0017] The phosphorus-containing organic material may include at least one selected from phytic acid, phytate, sodium hypophosphate, phosphoric acid, hexachlorophosphazene, hydroxyethylidene diphosphonic acid, and combinations thereof.

[0018] The nitrogen-containing and sulfur-containing organic material may include at least one selected from the group consisting of thiourea, ammonium thiocyanate, thioacetamide, and combinations thereof.

[0019] In one embodiment, the initiator may include a 3 ), ammonium persulfate ((NH 4 ) 2 S 2 O 8 ), zinc chloride (ZnCl 2 ), hydrogen peroxide (H 2 O 2 ), potassium permanganate (KMnO 4 ), sodium dichromate (Na 2 Cr 2 O 7 ), and at least one of a combination thereof.

[0020] In one embodiment, the precursor dispersion may contain 0.1 to 10 equivalents of the initiator based on the polymer raw material.

[0021] In one embodiment, the carbon material may include at least one selected from activated carbon, carbon black, carbon nanotubes, graphene, and combinations thereof.

[0022] In one embodiment, the carbon material may have mesopores, and the average diameter of the mesopores may be 2 nm to 50 nm.

[0023] In one embodiment, the carrier dispersion may be prepared by at least one method selected from ultrasonic dispersion, stirring, hydraulic high pressure homogenization, and a combination thereof.

[0024] The hydraulic high pressure homogenization may include the steps of preparing a fluid including a precursor polymer, carbon and a second organic solvent, and adjusting the pressure of the fluid to 100 to 3,500 bar at least once. g The step of dispersing the carbon material includes passing the fluid through a nozzle having a diameter of 50 μm to 200 μm at a flow rate of 100 to 2,000 ml / min.

[0025] In one embodiment, the intermediate may include 30 to 150 parts by weight, for example 100 parts by weight, of the precursor polymer, based on 100 parts by weight of the carbon material.

[0026] In one embodiment, the primary heat treatment may be performed in an inert atmosphere at a temperature within a range of ±50° C. relative to the melting point Tm of the precursor polymer for 0.1 to 5 hours.

[0027] In one embodiment, the primary heat treatment may be performed at a temperature of 200° C. to 300° C. for 0.1 to 5 hours in an inert atmosphere.

[0028] In one embodiment, the secondary heat treatment may be performed at a temperature of 600° C. to 1,200° C. for 1 to 12 hours.

[0029] In one embodiment, the longitudinal crystal size (Lc) of the carbonized layer may be equal to or greater than 3.0 nm.

[0030] In one embodiment, the longitudinal crystal size (Lc) of the carbonized layer may be equal to or greater than 2.0 nm.

[0031] In one embodiment, the catalytic metal may include at least one selected from platinum (Pt), gold (Au), silver (Ag), rhodium (Rh), nickel (Ni), cobalt (Co), iron (Fe), palladium (Pd), copper (Cu), iridium (Ir), osmium (Os), molybdenum (Mo), vanadium (V), and combinations thereof.

[0032] In one embodiment, the catalytic metal may be included in an amount of 10 to 50 parts by weight based on 100 parts by weight of the catalyst.

[0033] According to one embodiment of the present disclosure, a fuel cell catalyst may include: a carbon support including a carbon material and a carbonized layer covering at least a portion of a surface of the carbon material; and a catalytic metal uniformly dispersed in the carbonized layer. The carbonized layer may include at least one heteroatom selected from sulfur (S), nitrogen (N), phosphorus (P) and combinations thereof.

[0034] The catalytic metal can be uniformly dispersed on the carbonized layer through chemical bonding with heteroatoms.

[0035] In one embodiment, the thickness of the carbonized layer may be 3.0 nm or more. In addition, the longitudinal crystal size (Lc) of the carbonized layer may be 2.0 nm or more.

[0036] In one embodiment, the carbon material may have mesopores, and the average diameter of the mesopores may be 2 nm to 50 nm. The catalytic metal may be uniformly dispersed on the outer surface and the inner surface of the carbon material.

[0037] According to one embodiment of the present disclosure, after the conductive polymer containing heteroatoms is composited with the carbon support, a heteroatom-doped carbonized layer can be provided on the surface of the carbon material through primary and secondary heat treatment, thereby providing a carbon support with enhanced binding force with the catalytic metal and improved durability. In this way, an anchoring effect of strong binding between the doped heteroatoms and the catalytic metal can be induced to enhance the catalytic binding force, and at the same time, the carbon layer on the surface of the carbon support can be enhanced to enhance the corrosion resistance of the carbon.

[0038] The advantages of the present disclosure are not necessarily limited to the advantages described above. The advantages of the present disclosure can be understood to include the advantages that can be inferred from the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is a schematic diagram of an intermediate according to one embodiment of the present disclosure;

[0040] Figure 2 is a schematic diagram of an intermediate including a mesoporous carbon material according to one embodiment of the present disclosure;

[0041] Figure 3 is a schematic diagram of a carbon support according to one embodiment of the present disclosure;

[0042] Figure 4 is a schematic diagram of a carbon support including a mesoporous carbon material according to one embodiment of the present disclosure;

[0043] Figure 5 is a schematic diagram of an intermediate according to one embodiment of the present disclosure;

[0044] Figure 6 is a schematic diagram of a catalyst including a mesoporous carbon material according to one embodiment of the present disclosure;

[0045] Figure 7 is a schematic diagram of a crystal structure of carbon according to one embodiment of the present disclosure;

[0046] Figure 8 The S of Example 1, Comparative Example 1 and Comparative Example 2 according to one embodiment of the present disclosure are shown. 2p XPS results;

[0047] Fig. 9is a transmission electron microscope (TEM) image of Example 1 according to one embodiment of the present disclosure;

[0048] Fig.10 shows the energy dispersive X-ray spectroscopy (EDS) analysis result of Example 1 according to one embodiment of the present disclosure;

[0049] Fig.11 is a TEM image of Comparative Example 1 according to one embodiment of the present disclosure;

[0050] Fig.12 is a TEM image of Comparative Example 2 according to one embodiment of the present disclosure;

[0051] Fig.13 Showing XRD analysis results of Example 1 and Comparative Example 1 according to one embodiment of the present disclosure;

[0052] Fig.14 The 77K / N of Example 1 and Comparative Example 1 according to one embodiment of the present disclosure are shown. 2 Gas adsorption analysis results;

[0053] Fig.15 Showing porosity analysis results of Example 1 and Comparative Example 1 according to one embodiment of the present disclosure;

[0054] Fig.16 Showing durability test conditions of membrane electrode assemblies (MEAs) of Application Example 6 and Comparative Example 4 according to one embodiment of the present disclosure;

[0055] Fig.17 shows the electrochemical performance of each MEA of Application Example 6 and Comparative Example 4 before and after the durability test according to one embodiment of the present disclosure; and

[0056] Fig.18 Deterioration rates of each MEA of Application Example 6 and Comparative Example 4 before and after the durability test according to one embodiment of the present disclosure are shown. DETAILED DESCRIPTION

[0057] The above and other features and advantages of the present disclosure will be easily understood from the following example embodiments associated with the accompanying drawings. However, the embodiments of the present disclosure are not necessarily limited to the example embodiments described herein, and may be implemented in other forms. The example embodiments described herein are provided to make the present disclosure more comprehensive and complete, and to enable the spirit of the present disclosure to be fully conveyed to those skilled in the art.

[0058] Throughout the accompanying drawings, the same elements may be represented by the same reference numerals. In the accompanying drawings, for clarity of the present disclosure, the size of the structure is larger than the actual size. The terms "first", "second", etc. used in the specification may be used to describe various components, but the components should not be interpreted as necessarily being limited by such terms. Such terms may be used for the purpose of distinguishing a component from another component. For example, without departing from the scope of the present disclosure, a first component may be referred to as a second component, and a second component may also be referred to as a first component. As used herein, unless the context clearly indicates otherwise, the singular forms "one", "one", and "the" may also include plural forms.

[0059] It is further understood that the terms "comprises," "comprising," "containing," or "having" when used in this specification specify the presence of the features, regions, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and / or combinations thereof. It is also understood that when an element such as a layer, film, region, or sheet is referred to as being "above" another element, it can be directly on the other element, or an intermediate element can exist between them. Similarly, when an element such as a layer, film, region, or sheet is referred to as being "below" another element, it can be directly below the other element, or an intermediate element can exist between them.

[0060] Unless otherwise stated, all numbers, values ​​and / or expressions used herein to represent the amounts of components, reaction conditions, polymer compositions and mixtures are considered approximate values, including the various uncertainties that inherently affect the measurements when obtaining these values, and are therefore understood to be modified by the term "about" in all cases. In addition, when a numerical range is disclosed in this specification, the range is continuous and includes all values ​​from the minimum value of the range to its maximum value, unless otherwise stated. In addition, when the range involves integer values, all integers from the minimum value to the maximum value are included, unless otherwise stated.

[0061] In this specification, when describing the range of a variable, the variable can be understood to include all values ​​within the range, including the endpoints of the range. For example, the range "5 to 10" can be understood to include not only the values ​​5, 6, 7, 8, 9 and 10, but also any sub-ranges thereof, such as 6 to 10, 7 to 10, 6 to 9, 7 to 9, and any values ​​between the integers within the category of the range, such as 5.5, 6.5, 7.5, 5.5 to 8.5 and 6.5 to 9. It can also be understood that, for example, the range of "10% to 30%" includes values ​​such as 10%, 11%, 12%, 13% and all integers not exceeding 30%, and any sub-ranges, such as 10% to 15%, 12% to 18%, 20% to 30%, and any values ​​between reasonable integers within the category of the range, such as 10.5%, 15.5%, 25.5%, etc.

[0062] Method for producing fuel cell catalyst

[0063] Figure 1 is a schematic diagram of an intermediate according to one embodiment of the present disclosure.

[0064] A method for manufacturing a fuel cell catalyst according to an embodiment of the present disclosure may include: synthesizing a precursor polymer 20; preparing a carrier dispersion including the precursor polymer 20 and a carbon material 10; preparing an intermediate having a structure in which the surface of the carbon material 10 is coated with the precursor polymer 20; fixing the precursor polymer 20 on the surface of the carbon material 10 by performing a primary heat treatment on the intermediate; converting the precursor polymer 20 into a carbonized layer 20' by performing a secondary heat treatment on the intermediate to prepare a carbon carrier; and introducing a catalytic metal 30 into the carbonized layer 20' to produce a catalyst. The carbonized layer 20' may contain a heteroatom selected from sulfur (S), nitrogen (N), phosphorus (P), and a combination thereof.

[0065] The fuel cell catalyst obtained by the manufacturing method may have a carbonized layer 20' doped with more foreign atoms than conventional fuel cell catalysts. Therefore, in one embodiment, the bonding force between the catalytic metal 30 and the carbon support and the durability of the carbon support can be improved.

[0066] The manufacturing method of the embodiment will be described in more detail below.

[0067] The step of synthesizing the precursor polymer may include dissolving a polymer raw material derived from the precursor polymer 20 in a first organic solvent. The polymer raw material may include one selected from nitrogen-containing organic materials, sulfur-containing organic materials, nitrogen-containing and sulfur-containing organic materials, phosphorus-containing organic materials, and polymers thereof.

[0068] The nitrogen-containing organic material may include one selected from the group consisting of pyrrole, guanine, adenine, purine, melamine, urea, pyridine, aniline, dicyandiamide, ethylenediamine, ethylenediaminetetraacetic acid (EDTA), and combinations thereof.

[0069] The sulfur-containing organic material may include one selected from dibenzyl disulfide, thiophene, 2,2-dithiophene, p-toluenesulfonic acid, 2-thiophene methanol, and combinations thereof.

[0070] The nitrogen-containing and sulfur-containing organic material may include one selected from the group consisting of thiourea, ammonium thiocyanate, thioacetamide, and combinations thereof.

[0071] The phosphorus-containing organic material may be selected from one of phytic acid, phytate, sodium hypophosphate, phosphoric acid, hexachlorocyclotriphosphazene, hydroxyethylidene diphosphonic acid, and combinations thereof.

[0072] In the exemplary embodiment, the first organic solvent is not particularly limited as long as it can dissolve the polymer raw material. For example, an aromatic organic solvent such as dichloromethane, benzene, toluene, etc. may be used, or a non-polar organic solvent may be used.

[0073] Next, a precursor dispersion may be prepared by adding an initiator to the first organic solvent in which the polymer raw material is dissolved. Examples of the initiator may include a ferric chloride (FeCl 3 ), ammonium persulfate ((NH 4 ) 2 S 2 O 8 ), zinc chloride (ZnCl 2 ), hydrogen peroxide (H 2 O 2 ), potassium permanganate (KMnO 4 ), sodium dichromate (Na 2 Cr 2 O 7 ), and one of the combinations thereof.

[0074] The precursor dispersion may contain 0.1 to 10 equivalents of initiator based on the polymer raw material. When the amount of the initiator is less than 0.1 equivalents, the reaction rate may be low and the degree of polymerization may not be significant. When the amount of the initiator is greater than 10 equivalents, it may be difficult to control the polymerization rate, resulting in reduced efficiency.

[0075] Next, an initiation reaction may occur in a precursor dispersion containing a first organic solvent, a polymer raw material, and an initiator, thereby performing a polymerization reaction. Specifically, the precursor dispersion may be stirred at 0° C. to 80° C. for 3 to 48 hours. When the stirring temperature of the precursor dispersion is lower than 0° C. or the stirring time is shorter than 3 hours, polymerization may not occur sufficiently. When the stirring temperature is higher than 80° C. or the stirring time exceeds 48 hours, the uniformity of the polymer produced by the polymerization may be reduced, and the synthesis efficiency may be poor.

[0076] After the precursor dispersion is stirred and polymerized, the reaction product may be filtered, washed and dried. Thus, a precursor polymer may be obtained. Washing may be performed at least twice, each time the reaction product may be washed with acetone and then with ethanol. Drying may be performed in a vacuum oven at a temperature of 60° C. to 100° C.

[0077] If, unlike the method used in certain embodiments of the present disclosure, the polymer raw material containing heteroatoms is directly coated on the surface of the carbon material 10, the polymer raw material has a low boiling point and is easily volatile, and the fixation rate of the polymer raw material on the surface of the carbon material 10 will be low, so the doping efficiency will be low.

[0078] According to an embodiment of the present disclosure, heteroatoms can be introduced into the surface of the carbon material 10 using the non-volatile precursor polymer 20, rather than directly doping the heteroatoms on the surface of the carbon material 10. Therefore, in one embodiment, the amount of heteroatoms doped on the surface of the carbon material 10 can be greatly increased.

[0079] In one embodiment, the precursor polymer 20 may include a conductive polymer. When the precursor polymer 20 is a conductive polymer, the uniform coating and surface fixation rate of the carbon material 10 can be improved due to the good carbon-polymer compatibility. Therefore, the conductive polymer can be appropriately used for the precursor polymer 20. In addition, the π-π interaction between the conjugated π orbital of the conductive polymer and the π orbital of the carbon material 10 can enhance the binding force, thereby improving the fixation rate of the surface dopant. Of course, this does not mean that the precursor polymer 20 must be a conductive polymer.

[0080] After the precursor polymer is synthesized by the above method, a carrier dispersion containing the precursor polymer 20 and the carbon material 10 can be prepared. The carrier dispersion can be prepared by at least one method selected from ultrasonic dispersion, stirring, hydraulic high-pressure homogenization, and a combination thereof. By dispersing the carrier dispersion using the above method, uniform dispersion of the precursor polymer 20 and the carbon material 10 and an increase in surface area can be achieved.

[0081] In one embodiment, the hydraulic high pressure homogenization may include the steps of preparing a fluid including the precursor polymer 20, the carbon material 10 and the second organic solvent, and adjusting the pressure of the fluid to 100 to 3,500 bar.g and passing the fluid through a nozzle having a diameter of 50 μm to 200 μm at a flow rate of 100 to 2,000 ml / min to disperse the carbon material 10.

[0082] See also Figure 1 , using hydraulic high pressure homogenization, the precursor polymer 20 and the carbon material 10 can be dispersed more uniformly, so that a carrier dispersion with an increased surface area can be obtained.

[0083] In an embodiment, the carrier dispersion may include 5 to 300 parts by weight of the precursor polymer 20 based on 100 parts by weight of the carbon material 10. Preferably, the content of the precursor polymer 20 may be 30 to 150 parts by weight, for example, 100 parts by weight. When the content of the precursor polymer 20 is less than 30 parts by weight, a carbon carrier with a low heteroatom doping rate may be produced. When the content of the precursor polymer 20 is greater than 150 parts by weight, the porosity of the carbon carrier may be reduced due to excessive heteroatom content.

[0084] Examples of the carbon material 10 may include one selected from activated carbon, carbon black, carbon nanotubes, graphene, and combinations thereof. The carbon material 10 has mesopores (MP), and the average diameter of the mesopores (MP) may be 2 nm to 50 nm.

[0085] Figure 2 and Figure 4 An intermediate including a carbon material 10 having mesopores (MP) formed therein is schematically shown. Figure 6 As described later, the catalytic metal 30 may be introduced into the mesopores (MP) formed in the carbon material 10 of the carbon carrier. When the average diameter of the mesopores is less than 2 nm, there may not be enough space in the carbon carrier to accommodate the catalytic metal 30. When the average diameter of the mesopores exceeds 50 nm, the specific surface area of ​​the carbon material 10 is reduced, so that a small amount of the catalytic metal 30 is introduced into the carbon carrier.

[0086] See also Figure 2 , after the carrier dispersion is prepared as described above, a solvent removal process may be performed to produce an intermediate including the precursor polymer 20 coated on the surface of the carbon material 10. The solvent removal process may be an evaporation or drying process conventionally used to remove an organic solvent. For example, a rotary evaporator may be used to remove the solvent from the carrier dispersion, and the solvent-free residue may be dried in a vacuum oven at a temperature of 60° C. to 100° C. to obtain an intermediate. Herein, the intermediate is described such that the surface of the carbon material 10 is coated, but the term "surface of the carbon material" may include the inner surface of the mesopores of the carbon material 10 as well as the outer surface of the carbon material 10, such as Figure 2 , Figure 4 and Figure 6 shown.

[0087] Next, the intermediate may be subjected to a primary heat treatment to fix the precursor polymer 20 to the surface of the carbon material 10. In this case, the primary heat treatment may be performed within a temperature range of ±50°C relative to the melting point Tm of the precursor polymer 20.

[0088] When the temperature of the primary heat treatment is lower than -50°C relative to the melting point Tm of the precursor polymer 20, the precursor polymer 20 may not be sufficiently relaxed and a small structural change may occur, resulting in a weak effect of fixing the precursor material 20 to the surface of the carbon material 10. When the temperature of the primary heat treatment is higher than +50°C relative to the melting point Tm of the precursor polymer 20, the precursor polymer 20 may decompose or may be undesirably carbonized.

[0089] The range of ±50° C. with respect to the melting point Tm may vary depending on the type of the precursor polymer 20 , but for example, the temperature of the primary heat treatment may be in the range of 200° C. to 300° C.

[0090] In addition, the primary heat treatment may be performed in an inert atmosphere for 0.1 to 5 hours. When the time of the primary heat treatment is shorter than 0.1 hours, the precursor polymer 20 may not be sufficiently relaxed and may undergo minor structural changes, resulting in a weaker effect of fixing the precursor material 20 to the surface of the carbon material 10. When the time of the primary heat treatment is longer than 5 hours, the precursor polymer 20 may decompose or undesirably carbonize.

[0091] On the other hand, the inert atmosphere can be formed by an inert gas. The type of the inert gas is not particularly limited, but nitrogen (N 2 ) or Group 18 gases.

[0092] Figure 3 and Figure 4 1 is a schematic diagram of a carbon support according to one embodiment of the present disclosure and a carbon support including a carbon material 10 having mesopores (MP) according to one embodiment of the present disclosure.

[0093] After the precursor polymer 20 is fixed on the carbon material 10 by the primary heat treatment, a secondary heat treatment may be performed. The precursor polymer 20 contained in the intermediate may be carbonized by the secondary heat treatment and converted into a carbonized layer 20', such as Figure 2 and Figure 4 As shown. Herein, the term "carbonization" may refer to a process in which functional groups contained in the precursor polymer 20 are removed and converted into carbon (C).

[0094] In one embodiment, the secondary heat treatment may be performed at 600° C. to 1,200° C. for 1 to 12 hours. When the secondary heat treatment is performed at a temperature below 600° C. or for less than 1 hour, the carbonization effect may be reduced. When the secondary heat treatment is performed at a temperature above 1,200° C. or for more than 12 hours, heteroatoms may be removed, resulting in reduced doping effect.

[0095] The secondary heat treatment may be performed in substantially the same inert atmosphere as described above, ie, the same inert atmosphere as that of the primary heat treatment, and thus a repeated description will be omitted.

[0096] In one embodiment, the thickness of the carbonized layer 20' formed by the secondary heat treatment may be 3 nm or greater. The thickness of the carbonized layer 20' may be observed using a microscope, such as a transmission electron microscope (TEM) or a scanning electron microscope (SEM). When the thickness of the carbonized layer 20' is less than 3 nm, the durability of the carbon support may be reduced.

[0097] The upper limit of the thickness of the carbonized layer 20 ′ is not particularly limited, and may be, for example, 100 nm or less.

[0098] Figure 7 is a reference diagram showing a longitudinal crystal size of the carbonized layer 20 ′. In one embodiment, the longitudinal crystal size Lc of the carbonized layer 20 ′ may be greater than or equal to 2.0 nm.

[0099] The longitudinal crystal size Lc of the carbonized layer 20' can be calculated by the Scherrer equation. The Scherrer equation is a formula that relates the size of microcrystals in a solid crystal to the peak width of a diffraction pattern, and can be written as the following formula 1.

[0100] [Formula 1]

[0101]

[0102] Where: τ is the average size of the crystal, K: is the shape factor, λ is the X-ray wavelength, β is the half width of the maximum intensity peak, and θ is the X-ray incident angle.

[0103] When the longitudinal crystal size of the carbonized layer 20' is less than 2 nm, the durability of the carbon support may be reduced. The longitudinal crystal size of the carbonized layer 20' is not particularly limited and may be, for example, 100 nm or less.

[0104] The carbonized layer 20' according to an embodiment of the present disclosure may be formed of a precursor polymer 20. Therefore, the carbonized layer 20' may include one hetero atom selected from sulfur (S), nitrogen (N), phosphorus (P), and a combination thereof.

[0105] Figure 5 and Figure 6 Schematic diagrams of a catalyst in which a catalytic metal 30 is supported on a carbon support according to an embodiment of the present disclosure and a catalyst in which a catalytic metal 30 is supported on both the inner and outer sides of a carbon support including a carbon material 10 having mesopores (MP) according to an embodiment of the present disclosure.

[0106] After the carbon support is prepared by the secondary heat treatment, the catalytic metal 30 can be introduced into the carbon support to synthesize a fuel cell catalyst. As long as the salt of the catalytic metal 30 can interact with the carbonized layer 20' of the carbon support, any method of introducing the catalytic metal 30 into the carbon support can be used without limitation. For example, an impregnation method, a polyol method, an incipient wetness impregnation method, etc. can be used.

[0107] The heteroatoms doped on the carbonized layer 20' can strongly interact with the catalytic metal 30, thereby improving the binding force and dispersion (anchoring effect) between the catalytic metal 30 and the carbon support. Therefore, in one embodiment, although the fuel cell including the fuel cell catalyst is repeatedly charged and discharged, the catalytic metal 30 may not be easily dissolved, and the dissolution durability can be improved.

[0108] In an embodiment, the catalytic metal may include one selected from platinum (Pt), gold (Au), silver (Ag), rhodium (Rh), nickel (Ni), cobalt (Co), iron (Fe), palladium (Pd), copper (Cu), iridium (Ir), osmium (Os), molybdenum (Mo), vanadium (V), and combinations thereof. Herein, the term "combination" may refer to an alloy of the catalytic metal.

[0109] In one embodiment, the content of the catalytic metal 30 may be 1 wt% to 99 wt% based on the total weight of the catalyst. Preferably, the content of the catalytic metal 30 may be 10 wt% to 50 wt%. When the content of the catalytic metal 30 is less than 10 wt%, the density of the catalytic metal 30 in the catalyst may be low. When the content of the catalytic metal 30 exceeds 50 wt%, the distance between the catalytic metal particles 30 is short, and the excessive catalytic metal 30 may make it difficult to induce the combination between the heteroatoms and the catalytic metal particles 30, thereby possibly reducing the durability of the catalyst.

[0110] Hereinafter, a fuel cell catalyst embodiment manufactured by the above-described method embodiment will be described.

[0111] Fuel cell catalysts

[0112] A fuel cell catalyst according to an embodiment of the present disclosure may include: a carbon support including a carbon material 10 and a carbonized layer 20' covering at least a portion of a surface of the carbon material 10; and a catalytic metal 30 uniformly dispersed in the carbonized layer 20'. The carbonized layer 20' may contain at least one heteroatom selected from sulfur (S), nitrogen (N), phosphorus (P), and combinations thereof.

[0113] The carbonized layer 20' containing heteroatoms can be formed by the following steps: preparing a carrier dispersion including a precursor polymer 20 and a carbon material 10, fully dispersing the carrier dispersion by ultrasonic dispersion, stirring or hydraulic high-pressure homogenization to prepare an intermediate, and then subjecting the intermediate to primary heat treatment and secondary heat treatment. Therefore, the heteroatoms can be uniformly dispersed on the surface of the carbonized layer 20'. At this time, the heteroatoms doped on the carbonized layer 20' can strongly interact with the catalytic metal 30, thereby improving the binding force and dispersibility (anchoring effect) between the catalytic metal 30 and the carbon carrier.

[0114] In one embodiment, since the fuel cell catalyst may be substantially the same as the catalyst prepared according to the above-mentioned fuel cell catalyst manufacturing method, a repeated detailed description will be omitted.

[0115] Other forms of other embodiments of the present disclosure will be described in more detail in conjunction with the following examples. The following examples (ie, exemplary embodiments) are only used to help understand the present disclosure and are not intended to limit the scope of the present disclosure.

[0116] Example 1

[0117] 1) 0.84 g of thiophene as a polymer raw material was dissolved in 100 mL of dichloromethane prepared as a first organic solvent. 9.72 g of ferric chloride (FeCl 3 ) as an initiator was dissolved in 100 mL of acetonitrile, and the mixture was mixed with a first organic solvent in which thiophene was dissolved, thereby preparing a precursor dispersion. The precursor dispersion was reacted at 25° C. for 24 hours (polymerization reaction), and then the reaction mixture was filtered and washed three times with acetone and ethanol in sequence. The reaction product was dried in a vacuum oven at 80° C. to obtain a polymer precursor (Pth, polythiophene).

[0118] Here, since the molecular weight of thiophene as the polymer raw material is 84.14 g / mol, the number of moles of reaction is 0.01 mol. In addition, since FeCl 3 The molecular weight of is 162.2 g / mol, so the number of reaction moles is 0.06 mol. Therefore, the equivalent of the added initiator is 6 relative to the polymer raw material.

[0119] 2) 0.5 g of the precursor polymer (polythiophene) was added to 100 ml of tetrahydrofuran (THF) as the second organic solvent, and the mixture was stirred with a magnetic bar. 0.5 g of ordered mesoporous activated carbon was added to the mixture as the carbon material 10, and the solution was ultrasonically treated for 30 minutes to prepare a carrier dispersion. The carrier dispersion was then stirred for 12 hours, and the second organic solvent was removed by a rotary evaporator. The dispersion from which the second organic solvent was removed was dried in a vacuum oven at 80° C. for 3 hours to prepare an intermediate.

[0120] 3) The intermediate is subjected to a primary heat treatment at 250° C. for 1 hour to obtain an intermediate in which the precursor polymer 20 is fixed on the carbon material 10. The primary heat treatment is performed under argon (Ar) conditions.

[0121] 4) The intermediate product subjected to the primary heat treatment was subjected to secondary heat treatment at 800° C. for 3 hours to carbonize the precursor polymer 20. As a result, a carbon support having a carbonized layer 20 ′ formed on the carbon material 10 was synthesized. The secondary heat treatment was performed under argon (Ar) conditions.

[0122] Example 2

[0123] A carbon support was synthesized in the same manner as in Example 1, except that 1.0 g of a precursor polymer (polythiophene) was added during the preparation of the support dispersion.

[0124] Example 3

[0125] A carbon support was synthesized in the same manner as in Example 1, except that a secondary heat treatment was performed at 1000° C. for 3 hours.

[0126] Example 4

[0127] The carbon support was synthesized in the same manner as in Example 1, except that pyrrole was introduced instead of thiophene during the synthesis of the precursor polymer 20 to synthesize polypyrrole as the precursor polymer 20 .

[0128] Example 5

[0129] 1) 0.84 g of thiophene as a polymer raw material was dissolved in 100 mL of dichloromethane prepared as a first organic solvent. 9.72 g of ferric chloride (FeCl 3 ) as an initiator was dissolved in 100 mL of acetonitrile, and the mixture was mixed with a first organic solvent in which thiophene was dissolved, thereby preparing a precursor dispersion. The precursor dispersion was reacted at 25° C. for 24 hours (polymerization reaction), and then the reaction mixture was filtered and washed three times with acetone and ethanol in sequence. The reaction product was dried in a vacuum oven at 80° C. to obtain a precursor polymer (Pth, polythiophene).

[0130] In addition, in the synthesis process of the precursor polymer 20 , polypyrrole was synthesized as the precursor polymer 20 by adding pyrrole instead of thiophene.

[0131] 2) A carbon support was synthesized in the same manner as in Example 1, except that polythiophene and polypyrrole were synthesized as the precursor polymer 20, and in the process of preparing the support dispersion, 0.5 g of polythiophene, 1.0 g of polypyrrole and 1.0 g of the carbon material 10 were added.

[0132] Example 6

[0133] A solution of the catalytic metal 30 is prepared by dissolving catalytic platinum (Pt) in ethylene glycol as a solvent. Next, the synthesized carbon support is added to the solution of the catalytic metal 30. Here, when the carbon support is 100 parts by weight, the catalytic platinum is 30 parts by weight. The solution containing the catalytic platinum and the carbon support is dried to obtain a fuel cell catalyst.

[0134] Comparative Example 1

[0135] The mesoporous carbon material 10 which is not doped with heteroatoms by using the precursor polymer 20 is prepared as a carbon support.

[0136] Comparative Example 2

[0137] 0.5 g of thiophene that has not been subjected to a polymerization process was mixed with 0.5 g of the mesoporous carbon material 10, and then the mixture was heat-treated at 800° C. for 3 hours to synthesize a carbon support having the carbon material 10 directly doped with heteroatoms (S). The secondary heat treatment was performed under argon (Ar) conditions.

[0138] Comparative Example 3

[0139] Unlike the wet synthesis of the carbon support by preparing an intermediate using the first organic solvent and the second organic solvent in Example 1, the carbon support having the carbonized layer 20' formed thereon was dry synthesized by injecting 1.0 g of thiourea and 1.0 g of the carbon material 10 into a planetary mill and heat treating them at 800°C for 3 hours.

[0140] Comparative Example 4

[0141] A fuel cell catalyst was synthesized in the same manner as in Example 6 above, except that 30 parts by weight of catalytic platinum (Pt) was introduced into the carbon support prepared according to Comparative Example 1 above.

[0142] Experimental Example 1-Surface Composition Analysis Results

[0143] In order to determine the surface composition of each carbon support prepared according to Examples 1 to 5 and Comparative Examples 1 to 3, S2pXPS analysis was performed. Figure 8 And as shown in Table 1.

[0144]

Table 1

[0145]

[0146] Refer to Table 1 and Figure 8 It can be seen that the peak intensity value of Example 1 is higher than that of Comparative Example 2 of the prior art. That is, a higher value indicates that the doping amount of heteroatom sulfur (S) in the carbonized layer 20' is significantly increased. In addition, Example 4 confirms that doping with nitrogen (N) is also applicable, and Example 5 confirms that two or more types of heteroatoms can be doped.

[0147] Experimental Example 2 - Surface structure and composition analysis by TEM and EDS

[0148] The carbon support synthesized according to Example 1 was imaged by TEM and EDS, respectively. Fig. 9 and 10 The carbon supports synthesized according to Comparative Example 1 and Comparative Example 2 were imaged by TEM, as shown in FIG. Fig.11 and 12 shown.

[0149] In order to compare the doping content when heteroatoms are doped using the precursor polymer 20 and the doping content when heteroatoms are directly introduced, the EDS analysis results of Example 1 and Comparative Example 2 are shown in Table 2 below.

[0150]

Table 2

[0151]

[0152] refer to Fig. 9 , it can be seen that the average thickness of the carbonized layer 20' formed on the surface of the carbon material 10 is about 3nm or more. Fig.10 , it can be seen that the carbon support is uniformly doped with the heterogeneous element sulfur (S).

[0153] On the other hand, according to Fig.11 and Fig.12 The thickness of the carbonized layer 20' of the carbon supports of Comparative Examples 1 and 2 is less than 2 nm. In addition, according to Table 2 above, the doping amount of the heterogeneous element sulfur (S) in Comparative Example 2 is too small to be observed through the EDS image.

[0154] Compared with conventional carbon, Example 1 shows that the thickness of the graphite layer is significantly increased (>3 nm), and the EDS results of Example 1 show that sulfur (S) is uniformly distributed. In other words, uniform doping can be achieved by the method of the present disclosure.

[0155] Experimental Example 3 - Surface structure and composition analysis by XRD

[0156] XRD was performed to analyze the structure of the carbonized layer 20' of each carbon support. The Lc(002) value representing the longitudinal crystal size of carbon contained in the carbonized layer 20' was calculated by the Scherrer equation. Fig.13 And as shown in Table 3.

[0157]

Table 3

[0158] Classification Lc(002)(nm) Comparative Example 1 1.6 Comparative Example 2 1.6 Example 1 2.0 Example 2 2.5

[0159] According to Table 3 above, Comparative Example 2 is a sample directly doped with carbon (prior art), and the thickness of the carbonized layer 20' of Comparative Example 2 is no different from that of the conventional carbon sample (Comparative Example 1). However, the thickness of the carbonized layer 20' of Example 1 increases to 2.0 nm. In addition, depending on the amount of the added precursor polymer 20, the results of Example 2 show that the thickness increases up to 2.5 nm.

[0160] Experimental Example 4-Porosity Analysis

[0161] In order to analyze the surface porosity of the prepared carbon support, 77K / N2 gas adsorption analysis was performed on the above Example 1 and Comparative Example 1. The specific surface area was calculated using the Brunauer-Emmett-Teller (BET) equation. The total pore volume was obtained using the adsorption curve with a relative pressure as high as 0.990, and the mesopore volume (Vmeso) was obtained using the value of the desorption curve by the Barret-Joyner-Halenda (BJH) method. The mesoporosity was calculated by dividing the mesopore volume by the total pore volume and multiplying by 100 (percent). The results are shown in Figure 2. Fig.14 , Fig.15 As shown in Table 4.

[0162]

Table 4

[0163] sample <![CDATA[S BET (m 2 / g)]]> <![CDATA[V meso (cm 3 / g)]]> S content (wt.%) Lc(002)(nm) Comparative Example 1 700 1.69 - 1.6 Example 1 450 1.22 2.3 2.0 Example 2 100 0.61 5.6 2.5

[0164] Comparative Example 1 is a typical mesoporous carbon material 10, characterized in that mesopores are well developed. Example 1 shows that by doping with foreign element sulfur (S) (including carbonization), the porosity (including specific surface area mesopores) is reduced. This is because the carbonized layer 20' formed on the surface of the carbon material 10 during the intermediate carbonization process blocks the micropores of the carbon material 10, thereby reducing the specific surface area and strengthening the walls of the mesopores. This leads to a reduction in the size and volume of the mesopores.

[0165] When the amount of the added polymer is large as in Example 2, it is confirmed that the amount of heteroelemental sulfur (S) increases, but it is also confirmed that the porosity decreases. However, although the porosity of the carbon support decreases as in Example 2, since the doping amount of heteroatoms is relatively high compared to Example 1, the bonding with the catalytic platinum and the dispersibility of the catalytic platinum are improved. Therefore, it is expected that the catalyst durability performance and battery performance between the membrane electrode assembly (MEA) including the catalyst of Example 1 and the MEA including the catalyst of Example 2 may be similar.

[0166] Experimental Example 5-Analysis of MEA Cell Performance and Catalyst Durability

[0167] Nafion (DuPont) as an electrolyte membrane, an electrode slurry containing a fuel cell catalyst obtained according to Example 6 or Comparative Example 4, a CNT paper sheet as a gas diffusion layer (GDL), and a separator with a flow path were prepared. The electrode slurry was applied to both sides of the electrolyte membrane and then dried to form an electrode. A membrane electrode assembly (MEA) cell was prepared by sequentially stacking a gas diffusion layer and a separator with a flow path on the electrode.

[0168] MEA batteries Fig.16 A durability test of 10,000 charge and discharge operation cycles was carried out under the conditions of Fig.17 and Fig.18 The electrochemical performance and catalyst durability degradation rate before and after the durability test using the MEA of Example 6 and Comparative Example 4 are shown, respectively.

[0169] The battery performance evaluation results showed that the initial performance before and after S doping was comparable. This is believed to be due to the increased hydrophilicity of the carbon surface caused by S doping, which improved the performance despite the reduction in porosity.

[0170] It was observed that after the accelerated durability test induced Pt dissolution, the degradation rate of the S-doped carbon-supported catalyst (Example 6) was significantly improved compared with the conventional carbon-supported catalyst (Comparative Example 4), from 40% to 10%. The reason is believed to be that the strong Pt-heteroatom bonding has the effect of reducing Pt dissolution and reducing particle coarsening.

Claims

1. A method for producing a catalyst for a fuel cell, the method comprising: Synthesizing precursor polymers; preparing a support dispersion comprising the precursor polymer and a carbon material; preparing an intermediate configured such that a surface of the carbon material is coated with the precursor polymer; performing a primary heat treatment on the intermediate to fix the precursor polymer to the surface of the carbon material; subjecting the intermediate to a secondary heat treatment to convert the precursor polymer into a carbonized layer, thereby producing a carbon support; as well as The catalyst is synthesized by introducing a catalytic metal at the carbide layer, wherein the carbide layer contains heteroatoms selected from sulfur S, nitrogen N, phosphorus P, and combinations thereof. The method of claim 1 , wherein the precursor polymer comprises a conductive polymer.

3. The method according to claim 1, wherein the synthesis of the precursor polymer comprises: preparing a precursor dispersion by adding a polymer raw material and an initiator to a first organic solvent; and The process of initiating a reaction from the polymer raw material dissolved in the precursor dispersion and performing a polymerization reaction is carried out.

4. The method according to claim 3, wherein the polymerization reaction comprises stirring the precursor dispersion, wherein the stirring is performed at a temperature in the range of 0°C to 80°C for 3 to 48 hours. 5 . The method according to claim 4 , further comprising washing and drying, wherein the washing and the drying are both performed after the stirring.

6. The method of claim 3, wherein the polymer feedstock comprises a material selected from the group consisting of nitrogen-containing organic materials, sulfur-containing organic materials, nitrogen-containing and sulfur-containing organic materials, phosphorus-containing organic materials, and polymers thereof.

7. The method of claim 6, wherein the nitrogen-containing organic material comprises a material selected from the group consisting of pyrrole, guanine, adenine, purine, melamine, urea, pyridine, aniline, dicyandiamide, ethylenediamine, ethylenediaminetetraacetic acid (EDTA), and combinations thereof.

8. The method of claim 6, wherein the sulfur-containing organic material comprises a material selected from the group consisting of dibenzyl disulfide, thiophene, 2,2-dithiophene, p-toluenesulfonic acid, 2-thiophene methanol, and combinations thereof.

9. The method of claim 6, wherein the nitrogen-containing and sulfur-containing organic material comprises a material selected from the group consisting of thiourea, ammonium thiocyanate, thioacetamide, and combinations thereof.

10. The method of claim 6, wherein the phosphorus-containing organic material comprises a material selected from the group consisting of phytic acid, phytates, sodium hypophosphate, phosphoric acid, hexachlorocyclotriphosphazene, hydroxyethylidene diphosphonic acid, and combinations thereof.

11. The method according to claim 3, wherein the initiator comprises an initiator selected from ferric chloride FeCl3, ammonium persulfate (NH4)2S2O8, zinc chloride ZnCl2, hydrogen peroxide H2O2, potassium permanganate KMnO4, sodium dichromate Na2Cr2O7, and combinations thereof.

12. The method according to claim 3, wherein the precursor dispersion comprises 0.1 to 10 equivalents of an initiator based on the polymer raw material.

13. The method according to claim 1, wherein the carbon material comprises at least one selected from activated carbon, carbon black, carbon nanotubes, graphene, and combinations thereof. 14 . The method according to claim 1 , wherein the carbon material has mesopores, and wherein an average diameter of the mesopores is in a range of 2 nm to 50 nm.

15. The method of claim 1, wherein the carrier dispersion is prepared by a method selected from ultrasonic dispersion, stirring, hydraulic high pressure homogenization, and combinations thereof.

16. The method of claim 15, wherein the hydraulic high pressure homogenization comprises: preparing a fluid including the precursor polymer, the carbon material, and a second organic solvent; and The pressure of the fluid is adjusted to 100 to 3,500 bar at least once. g The carbon material is dispersed by passing the fluid through a nozzle having a diameter of 50 μm to 200 μm at a flow rate of 100 to 2,000 ml / min. 17 . The method according to claim 1 , wherein the intermediate comprises 100 parts by weight of the carbon material and 30 to 150 parts by weight of the precursor polymer.

18. The method according to claim 1, wherein the primary heat treatment is performed in an inert atmosphere at a temperature within a range of ±50°C relative to the melting point of the precursor polymer for 0.1 to 5 hours.

19. The method according to claim 1, wherein the primary heat treatment is performed in an inert atmosphere at a temperature ranging from 200°C to 300°C for 0.1 to 5 hours.

20. The method of claim 1, wherein the secondary heat treatment is performed at a temperature ranging from 600°C to 1,200°C for 1 to 12 hours.

21. The method according to claim 1, wherein the carbonized layer has a thickness of 3.0 nm or more.

22. The method according to claim 1, wherein a longitudinal crystal size of the carbonized layer is 2.0 nm or more.

23. The method of claim 1, wherein the catalytic metal comprises a metal selected from the group consisting of platinum (Pt), gold (Au), silver (Ag), rhodium (Rh), nickel (Ni), cobalt (Co), iron (Fe), palladium (Pd), copper (Cu), iridium (Ir), osmium (Os), molybdenum (Mo), vanadium (V), and combinations thereof.

24. The method according to claim 1, wherein the catalytic metal is contained in an amount of 10 to 50 parts by weight relative to 100 parts by weight of the catalyst.

25. A fuel cell catalyst comprising: A carbon support comprising a carbon material and a carbonized layer covering at least a portion of a surface of the carbon material; and a catalytic metal uniformly dispersed on the carbonized layer, The carbonized layer includes a heteroatom selected from sulfur (S), nitrogen (N), phosphorus (P), and combinations thereof.

26. The catalyst according to claim 25, wherein the catalytic metal is uniformly dispersed on the carbonized layer by chemically bonding with the heteroatom.

27. The catalyst according to claim 25, wherein the carbonized layer has a thickness of 3.0 nm or more.

28. The catalyst according to claim 25, wherein a longitudinal crystal size of the carbonized layer is 2.0 nm or more.

29. The catalyst according to claim 25, wherein the carbon material has mesopores, wherein an average diameter of the mesopores is in the range of 2 nm to 50 nm, and wherein the catalytic metal is uniformly dispersed on the outer surface and the inner surface of the carbon material.

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