Method for analyzing platinum distribution in platinum catalysts for fuel cells

Abstract

The present invention relates to a method for analyzing the distribution of platinum in a platinum catalyst for a fuel cell. The present invention provides, as an example, a method for analyzing the distribution of platinum in a platinum catalyst for a fuel cell, comprising: a first step of preparing a carbon support having a certain proportion of mesopores; a second step of manufacturing a platinum or platinum alloy catalyst using the carbon support prepared in the first step; a third step of measuring the proportion of mesopores in the catalyst using BET analysis on the platinum or platinum alloy catalyst manufactured through the second step; a fourth step of calculating the rate of variation of mesopores by comparing the proportion of mesopores measured in the third step with the proportion of mesopores of the carbon support prepared in the first step; and a fifth step of analyzing the distribution state of platinum within the pores (distribution status and distribution ratio) according to the rate of variation of mesopores obtained through the fourth step.

Description

Technology Field

[0001] The present invention relates to a method for analyzing platinum distribution, and more specifically, to a method for analyzing the distribution of platinum within pores of a platinum catalyst for a fuel cell. Background Technology

[0002] Platinum catalysts possess excellent catalytic activity and stability, making them widely used in automotive exhaust purification, petrochemicals, fuel cells, and hydrogen generation reactions. In particular, they are primarily used in fuel cell catalysts due to their high activity.

[0003] Recently, technologies are being researched to maintain or improve catalytic performance while reducing platinum usage, and the distribution and pore structure of nanoparticles have a direct impact on the performance and durability of the catalyst.

[0004] One method to measure the distribution and pore structure of these nanoparticles is to observe them using a transmission electron microscope (TEM). TEM has the advantage of enabling high-resolution observation, allowing for visual confirmation of whether platinum particles are located within the pores of the support.

[0005] As such, TEM is very useful for confirming the location and distribution of platinum particles, but there are difficulties such as the difficulty in preparing samples, the difficulty in obtaining other information, and the high cost of the equipment. Prior art literature

[0006] Republic of Korea Registered Patent No. 10-1033883 The problem to be solved

[0007] The present invention provides a method for analyzing the platinum distribution of a fuel cell platinum catalyst, wherein platinum or a platinum-containing alloy is synthesized in a certain ratio (5–95%), the distribution of platinum within the pores is estimated by analyzing the specific surface area and pore structure according to the gas adsorption method (BET, Brunauer-Emmett-Teller), and the platinum distribution of the fuel cell catalyst is analyzed accordingly. means of solving the problem

[0008] To solve the above problem, the present invention provides, as an embodiment, a method for analyzing the distribution of platinum in a platinum catalyst for a fuel cell, comprising: a first step of preparing a carbon support having a certain proportion of mesopores; a second step of manufacturing a platinum or platinum alloy catalyst using the carbon support prepared in the first step; a third step of measuring the proportion of mesopores of the catalyst using BET analysis on the platinum or platinum alloy catalyst manufactured through the second step; a fourth step of calculating the rate of variation of mesopores by comparing the proportion of mesopores measured in the third step with the proportion of mesopores of the carbon support prepared in the first step; and a fifth step of analyzing the distribution state of platinum within the pores according to the rate of variation of mesopores obtained through the fourth step.

[0009] At this time, the preparation of the platinum or platinum alloy catalyst in the second step above may use a method that includes a process of reducing metal particles using hydrogen or a process of reducing metal particles using a polyol.

[0010] Meanwhile, the analysis of the distribution state of platinum within the pore in the above 5th step may involve analyzing whether platinum is distributed within the pore and the distribution ratio. Effects of the invention

[0011] According to an embodiment of the present invention, by confirming that the ratio of mesopore volume in the gas adsorption method (BET) analysis results of a catalyst prepared using a carbon support having a mesopore ratio of 70 to 100% is maintained at 70 to 100%, it can be seen that the positions of platinum and platinum-containing alloy nanoparticles are located in the mesopores.

[0012] Furthermore, based on the distribution and pore structure of platinum and platinum-containing alloy nanoparticles derived from BET analysis results, an increase in reaction rate and efficiency can be predicted. In particular, this can contribute to higher performance in oxygen reduction reactions, hydrogen oxidation reactions, and other electrochemical reactions.

[0013] Furthermore, the interaction mechanisms of platinum and platinum-containing alloy nanoparticle distributions can be quantitatively analyzed, which enhances the reproducibility and efficiency of catalyst design. The ability to precisely analyze the impact of nanoparticle distribution within the pore structure on reaction pathways enables the rapid identification of optimized conditions for various catalytic applications. This increased analytical efficiency contributes to the design of new catalysts and the shortening of development cycles.

[0014] Other effects of the present invention will be clearly grasped and understood by experts or researchers in the art through the specific details described below or during the process of implementing the present invention. Brief explanation of the drawing

[0015] FIG. 1 is a flowchart illustrating a method for analyzing the platinum distribution of a platinum catalyst for a fuel cell according to an embodiment of the present invention. FIG. 2 is a diagram showing the results of measuring a platinum catalyst prepared according to an example using TEM. Specific details for implementing the invention

[0016] The features and effects of the present invention described above will become clearer through the following detailed description in conjunction with the attached drawings, and accordingly, a person skilled in the art to which the present invention pertains will be able to easily implement the technical concept of the present invention. Since the present invention is susceptible to various modifications and may take various forms, specific embodiments are illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to specific disclosed forms, and it should be understood that it includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the present invention. The terms used in this application are used merely to describe specific embodiments and are not intended to limit the present invention.

[0017] A method for analyzing the platinum distribution of a platinum catalyst for a fuel cell according to an embodiment of the present invention will be described in detail below with reference to the drawings.

[0018] A platinum distribution analysis method according to an embodiment of the present invention comprises: i) a first step of preparing a carbon support having a certain proportion of mesopores; ii) a second step of manufacturing a platinum catalyst using the carbon support; iii) a third step of measuring the pore distribution of the manufactured platinum catalyst; iv) a fourth step of comparing the pore distribution of the first step and the third step; and v) a fifth step of analyzing the distribution of platinum.

[0019] Each detailed step is explained below.

[0020] FIG. 1 is a flowchart illustrating a method for analyzing the platinum distribution of a platinum catalyst for a fuel cell according to an embodiment of the present invention.

[0021] In the first step, a carbon support having a certain proportion of mesopores is prepared (S10).

[0022] At this time, the proportion of mesopores in the pores can be 70–100%, and a carbon support with a mesopore proportion of 70–100% can be manufactured in various ways.

[0023] For example, as is known, hard template methods, soft template methods, chemical activation methods, gas activation methods, etc., can be used.

[0024] The hard template method uses templates such as silicates or metal oxides to create precise pore structures, while the soft template method uses surfactants or polymer materials to form mesopores with a simpler process.

[0025] Meanwhile, chemical activation methods treat carbon using activators at high temperatures, and gas activation can create pores using gases such as CO2 or H2O. Although these methods are relatively simple, they may have limitations in controlling the pore structure.

[0026] In addition, such carbon supports can also be prepared by purchasing commercial products. As described above, carbon supports with a mesopore ratio of 70 to 100% can be prepared using various methods.

[0027] Here, the carbon support serves to support the catalyst particles as a material that provides a high specific surface area and excellent conductivity. Carbon-based materials such as activated carbon, carbon black, carbon nanotubes, and graphene can be used as carbon supports, and known carbon blacks such as furnace black, acetylene black, vulcan carbon, and ketjen carbon can be used.

[0028] In the second step, a platinum catalyst is prepared using the carbon support prepared in the first step (S20).

[0029] Although there are various processes for manufacturing platinum catalysts, representative methods include reducing platinum particles using hydrogen or polyols.

[0030] The hydrogen reduction method is a process for preparing a catalyst by reducing a platinum precursor in a high-temperature hydrogen atmosphere. First, a support, such as carbon or a metal oxide, is prepared. Surface impurities are removed from the support through washing and drying processes, and chemical or heat treatments may be performed to improve surface properties if necessary. Subsequently, a solution prepared by dissolving a platinum precursor (e.g., chloroplatinic acid or platinum nitric acid) in a water or alcohol solvent is impregnated onto the support. During this process, the solution and the support are uniformly mixed so that the platinum precursor is evenly distributed across the surface and pores of the support.

[0031] After evaporating the solvent through drying and heat treatment of the impregnated support, the platinum ions are reduced to metallic platinum by heat treatment under a hydrogen atmosphere at a high temperature (300–500°C). During this process, platinum particles are attached to the surface of the support in a metallic form. Finally, the catalyst is washed to remove remaining impurities, and the catalyst preparation can be completed through drying and additional post-treatment.

[0032] The hydrogen reduction method has the advantage of a simple process, suitability for mass production, and the ability to relatively easily control the platinum content of the catalyst.

[0033] Meanwhile, the polyol method is a process for preparing a catalyst by reducing a platinum precursor at a low temperature using a reducing agent such as a polyhydric alcohol (e.g., ethylene glycol). In this method, a homogeneous solution is first prepared by dissolving the platinum precursor in a solvent and a reducing agent, such as ethylene glycol. When this solution is heated to a certain temperature (80–160°C), the reducing agent acts to produce platinum ions (Pt 2+ ) This metal platinum (Pt 0 It is reduced to ). During the reaction process, platinum particles are formed in nanometer size, and the reaction temperature, time, and concentration of the solution can be controlled to control particle size and shape.

[0034] During the reduction process, a material such as a carbon support is mixed to allow platinum particles to adhere to the surface of the support. Once the reaction is complete, the catalyst is filtered and washed to remove residual organic matter and impurities, and the catalyst preparation can be finished through drying and post-treatment.

[0035] The polyol method is carried out at low temperatures and has the advantage of being able to precisely control the size and distribution of platinum particles.

[0036] In this way, platinum catalysts can be prepared in various ways, and in the prepared platinum catalyst, platinum may be present on the surface of the carbon support or within the mesopores.

[0037] In the third step, the ratio of mesopores of the catalyst is measured using BET analysis on the platinum or platinum alloy catalyst produced through the second step (S30).

[0038] BET analysis assumes the phenomenon of gas adsorption onto a solid surface in multiple layers. The amount of gas adsorbed varies for each pore size (micropores, mesopores, macropores).

[0039] Micropores (pore size < 2 nm) and mesopores (2–50 nm) can be distinguished based on the amount of other gas molecules adsorbed. More gas molecules can be adsorbed when adsorbed into pores of an appropriate size, such as mesopores, and the mesopore ratio can be inferred from this data.

[0040] In the fourth step, the ratio of mesopores measured in the third step is compared with the ratio of mesopores of the carbon support prepared in the first step to calculate the rate of change of mesopores (S40).

[0041] The proportion of mesopores in the platinum catalyst produced at this stage may decrease compared to the initial proportion of mesopores in the carbon support, or the proportion of mesopores in the platinum catalyst may be similar to the initial proportion of mesopores in the carbon support. This rate of mesopore variation serves as a basis for inferring the distribution of platinum.

[0042] In the fifth step, the distribution state of platinum within the pore can be analyzed according to the fluctuation rate of the mesopore obtained through the fourth step (S50).

[0043] A large calculated variation rate generally indicates the presence of platinum particles on the surface of the carbon support. Platinum particles on the surface of the carbon support can block mesopores, which manifests as a reduction in mesopores in BET analysis. On the other hand, a small calculated variation rate generally indicates the presence of platinum particles within the mesopores. In other words, as platinum particles enter the mesopores, the mesopores can be measured to be equivalent to the original carbon support in BET analysis.

[0044] In this way, it is possible to analyze the presence and distribution ratio of platinum within the pores based on the variability rate of mesopores.

[0045] Meanwhile, platinum and platinum-containing alloy nanoparticles located in mesopores suppress aggregation and loss, and maintain a stable particle distribution, thereby enhancing the durability and stability of the catalyst even during long-term reaction processes. This enables the catalyst to maintain stable performance for an extended period without degradation. In particular, it effectively prevents long-term performance degradation even in high-load environments such as fuel cells.

[0046] Based on this, by analyzing the variation rate of the mesopores, it is possible to identify and select a desirable manufacturing method that positions platinum within the mesopores.

[0047] Next, an example of the method for analyzing the platinum distribution of a platinum catalyst for a fuel cell according to the present invention will be described. In the following examples, other processes are identical, but the method for manufacturing the platinum catalyst is different, and the platinum distribution analysis allows for determining which process is more suitable.

[0048] Example 1

[0049] 1) A commercial carbon support having 70~100% mesopores was prepared.

[0050] 2) Next, a platinum catalyst was prepared using the prepared carbon support in the following manner.

[0051] i) An additive for dispersing platinum in chloroplatinic acid (H2PtCl6) was dissolved in pure water and added, followed by dissolution. The dissolution temperature was 50°C and the time was 1 hour. Afterward, the solution was cooled and filtered to prepare a platinum precursor solution.

[0052] ii) Carbon black was ground with a hand mixer while carbon nanotubes (CNT) were added and mixed evenly to prepare a carbon support for use.

[0053] iii) Platinum precursor solution was introduced into the carbon support at a constant rate using a metering pump at room temperature to impregnate the carbon support with platinum.

[0054] iv) The impregnated catalyst was aged at room temperature (25℃) for 12 hours while stirring. During this time, the impeller speed of the impregnation reactor was maintained at 50 RPM.

[0055] v) The aged catalyst was dried at 150°C for 12 hours. During this drying process, the catalyst was stirred with an impeller in the atmosphere.

[0056] vi) Platinum was reduced on the support (Carbon Black) by hydrogen heat treatment of the dried catalyst. The heat treatment was performed at 400–500°C for 1–8 hours. A hydrogen atmosphere (300 mL / min) was maintained during the heat treatment. Afterward, the catalyst was cooled naturally to obtain a dry powder.

[0057] vii) The catalyst, after heat treatment, was placed in a 9% nitric acid solution, and acid treatment was performed at 80°C for 1 hour while stirring to remove residual additives. Additionally, the catalyst after acid treatment was washed with pure water. During washing, the pH of the catalyst was adjusted to 5.6 to 5.8.

[0058] viii) The washed catalyst was dried at 50 to 300°C in a nitrogen atmosphere for a certain period of time, then ground to finally obtain a dry powder-state platinum catalyst.

[0059] 3) The ratio of mesopores in the obtained platinum catalyst was measured through BET analysis.

[0060] 4) The measured mesopore ratio was found to be 70–100%, which is equivalent to the mesopore ratio of the carbon support initially provided. Accordingly, it can be analyzed that the supported platinum is distributed within the pores.

[0061] Example 2

[0062] 1) A commercial carbon support having 70~100% mesopores was prepared.

[0063] 2) Next, a platinum catalyst was prepared using the prepared carbon support in the following manner.

[0064] i) Carbon black was added to ethylene glycol and mixed. At this time, the mixture was dispersed using an ultrasonic disperser at a constant speed and for a specific time.

[0065] ii) The carbon black dispersed in the first stage was evenly dispersed through secondary high-pressure dispersion.

[0066] iii) A chloroplatinic acid (H2PtCl6) solution was added to a secondary dispersed carbon black solution to synthesize a catalyst solution in which platinum particles were supported on carbon black.

[0067] iv) The synthesized catalyst solution was filtered through a filter, and the filtered catalyst was washed with pure water.

[0068] v) The washed catalyst was dried and then ground into a powder.

[0069] vi) The dried powder was heat-treated and ground again to obtain a platinum catalyst in a dry powder state.

[0070] 3) The ratio of mesopores in the obtained platinum catalyst was measured through BET analysis.

[0071] 4) The measured BET was 0–30%, which is significantly lower than the ratio of mesopores in the carbon support provided initially. Accordingly, it can be analyzed that the supported platinum is distributed on the outer surface of the carbon support rather than inside the pores.

[0072] Verification of results

[0073] For the catalysts prepared according to the examples and comparative examples, the size of platinum particles was measured by XRD analysis and the degree of platinum dispersion was measured by TEM. As a result of the measurement, the size of the platinum particles is shown in Table 1 and the TEM diagram is shown in Figure 2.

[0074] Examples Comparative example XRD Size(nm) 2.0 2.0

[0075] As a result of the measurement, the platinum particle sizes of both the example and the comparative example were 2.0 nm, showing no significant difference. Example 1 is a type of hydrogen reduction method, and Example 2 is a type of polyol method; it was confirmed that both examples could form platinum particles of an equivalent level. However, as shown in Fig. 2, in the case of Example 1, the dispersion of platinum particles increased and it was confirmed that platinum was present within the mesopores, whereas in the case of Example 2, the dispersion of platinum particles was low and it was confirmed that platinum was present outside the carbon support. Accordingly, the same conclusion as the platinum distribution analysis method according to the present invention was obtained, and it was confirmed that the platinum distribution analysis method according to the present invention is useful.

[0076] Although the detailed description of the present invention described above has been explained with reference to preferred embodiments of the invention, those skilled in the art or those with ordinary knowledge in the relevant technical field will understand that various modifications and changes can be made to the present invention without departing from the spirit and technical scope of the invention as described in the claims set forth below.

Claims

Claim 1 A method for analyzing the distribution of platinum in a platinum catalyst for a fuel cell, comprising: a first step of preparing a carbon support having a certain proportion of mesopores; a second step of manufacturing a platinum or platinum alloy catalyst using the carbon support prepared in the first step; a third step of measuring the proportion of mesopores of the catalyst using BET analysis on the platinum or platinum alloy catalyst manufactured through the second step; a fourth step of calculating the rate of variation of mesopores by comparing the proportion of mesopores measured in the third step with the proportion of mesopores of the carbon support prepared in the first step; and a fifth step of analyzing the distribution state of platinum within the pores according to the rate of variation of mesopores obtained through the fourth step, wherein the analysis of the distribution state of platinum within the pores in the fifth step analyzes whether platinum is distributed within the pores and the distribution ratio according to the rate of variation of mesopores, and at the same time, by analyzing the rate of variation of mesopores of platinum catalysts manufactured by different manufacturing methods, a preferred manufacturing method in which platinum is located within the mesopores is specified. Claim 2 A method for analyzing the platinum distribution of a platinum catalyst for a fuel cell, wherein, in the first step, the preparation of a platinum or platinum alloy catalyst includes a process of reducing metal particles using hydrogen or a process of reducing metal particles using a polyol. Claim 3 delete

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