Porous carbon support and catalyst for fuel cell

Abstract

The present disclosure relates to a porous carbon body, and more specifically, to a porous carbon body satisfying surface area physical properties including pores having a size of 2 nm or more and 5 nm or less, surface area physical properties including pores having a size of 2 nm or more and 100 nm or less, and surface area physical properties including pores having a size of 2 nm or more and 100 nm or less. And a porous carbon body having three physical properties, which are physical properties on an incremental map of a map in which the value of the nitrogen adsorption isotherm is subtracted from the value of the nitrogen desorption isotherm according to the relative pressure in the nitrogen adsorption / desorption isotherm.

Description

Technical Field

[0001] The present invention relates to a porous carbon support and a catalyst for a fuel cell using the same.

[0002] The national research and development project supporting the present invention is as follows.

[0003] Project inherent number: 1711182201

[0004] Project Number: 2021M3H4A1A02049886

[0005] Department Name: Ministry of Science and ICT

[0006] Project Management (Professional) Agency Name: National Research Foundation of Korea

[0007] Research Project Name: Development of Nanomaterial Technologies / Leading

[0008] Research Topic Name: Development of Synthesis Technology for Highly Crystalline Porous Carbon Supports Based on Low-Temperature Processes

[0009] Contribution Rate: 0.5

[0010] Project Implementing Agency Name: The Carbon Studio Co., Ltd.

[0011] Research Period: January 1, 2023 to December 31, 2023

[0012] Project inherent number: 1415186363

[0013] Project Number: 20020437

[0014] Department Name: Ministry of Trade, Industry and Energy

[0015] Project Management (Professional) Agency Name: Korea Institute of Industrial Technology Evaluation and Planning

[0016] Research Project Name: Development of Nanofusion Innovative Product Technologies

[0017] Research Topic Name: Development of Hydrogen Electric Vehicle Fuel Cell Module Technology Based on the Production of Platinum Alloy Nanocatalysts with a Platinum Usage of 0.2 g / kW or Less in MEA

[0018] Contribution Rate: 0.5

[0019] Project Implementing Agency Name: The Carbon Studio Co., Ltd.

[0020] Research Period: January 1, 2023 to December 31, 2023 Background Art

[0021] As an energy source that can replace fossil fuels, polymer electrolyte membrane fuel cells (PEMFCs; Polymer Electrolyte Membrane Fuel Cells), which are highly energy-efficient and environmentally friendly, are attracting much attention.

[0022] As a power generation system that uses a catalyst to generate electricity through the electrochemical reaction of hydrogen and oxygen, a PEMFC has a structure of a unit cell stack including a membrane-electrode assembly (MEA; Membrane-Electrode Assembly) and a bipolar plate. The MEA has a structure in which a cation exchange membrane (collectively referred to as a polymer electrolyte membrane) is inserted between the anode and the cathode.

[0023] An important factor determining the performance of a fuel cell is the catalyst for the electrodes (anode, cathode) that form the MEA. Generally, platinum-based catalyst particles are supported on a porous carbon carrier for use.

[0024] The porous carbon carrier not only supports the catalyst particles but also affects the catalytic ability. For example, the loading amount of the catalyst particles is determined by the specific surface area of the carbon carrier, and the stability and durability of the entire fuel cell are also affected according to the degree of deterioration of the carbon carrier. Most importantly, the pore structure of the carbon carrier has a great influence on the dispersion degree of the supported catalyst particles, the size of the catalyst particles, the position of the catalyst in the carrier, the gas diffusion rate, the degree of flooding occurrence, the power generation performance according to the fuel cell operating conditions (for example, high-temperature and low-humidity conditions, etc.). Therefore, various studies aimed at controlling the pore size and structure of the carbon carrier are underway.

[0025] However, at present, there are not only multiple explanations that are mutually opposed regarding the favorable pore structure of the porous carbon carrier, but also no favorable pore structure has been established. Summary of the Invention

[0026]

Problems to be Solved

[0027] One aspect of the present disclosure is to provide a porous carbon body that can exhibit improved mass activity when used as a fuel cell catalyst support.

[0028] The subject matter of the present invention is not limited to the above. Those of ordinary skill in the art to which the present invention pertains can easily understand the additional subject matters of the present invention from the overall content of the present invention specification.

[0029]

Technical Solution

[0030] According to one aspect, the porous carbon body satisfies the following physical properties:

[0031] Physical property 1: The surface area of pores sized from 2 nm or more to less than 5 nm obtained from the nitrogen desorption isotherm by the BJH (Barrett-Joyner-Halenda) method based on the Harkins-Jura formula is 100 m2 / g to 500 m 2 / g,

[0032] Physical property 2: The surface area of pores sized from 2 nm or more to less than 100 nm obtained from the nitrogen desorption isotherm by the BJH method based on the Harkins-Jura formula is 200 m 2 / g to 1500 m 2 / g,

[0033] Physical property 3: The nitrogen adsorption / desorption isotherm has a hysteresis loop, and in the relative pressure range of 0.3 to 1.0, the graph of the value obtained by subtracting the value of the nitrogen adsorption isotherm from the value of the nitrogen desorption isotherm according to the relative pressure, that is, the increment graph has at least a first maximum point and a second maximum point, and the value of the first maximum point located at a lower relative pressure is less than the value of the second maximum point located at a higher relative pressure.

[0034] In a specific example, the maximum point ratio of the value of the first maximum point divided by the value of the second maximum point can be 0.10 to 0.95.

[0035] In a specific example, the first maximum point is in the range where the relative pressure P / P0 is 0.4 or more and less than 0.9, and the second maximum point can be in the range where the relative pressure P / P0 is 0.9 or more and less than 1.0.

[0036] In a specific example, the first maximum point is in the range where the relative pressure P / P0 is 0.45 or more and 0.80, and the second maximum point can be in the range where the relative pressure P / P0 is 0.93 or more and 0.98.

[0037] In a specific example, in the nitrogen adsorption / desorption isotherm, the area ratio of the hysteresis loop area in the relative pressure range of P / P0 from 0.9 to 1.0 divided by the hysteresis loop area in the relative pressure range of P / P0 from 0.4 to 0.9 can be 0.1 to 2.0.

[0038] In a specific example, the area ratio can be 0.1 to 1.5.

[0039] In a specific example, the porous carbon body may further satisfy the following physical property 4:

[0040] Physical property 4: Average interlayer spacing d measured by X-ray diffraction method 002 is 0.335 nm to 0.350 nm.

[0041] In a specific example, the porous carbon body may further satisfy the following physical property 5:

[0042] Physical property 5: Lattice constant L in the a-axis direction measured by X-ray diffraction method a is 4 nm to 12 nm.

[0043] In a specific example, the relative pressure P / P0 at the closing point of the hysteresis loop may be 0.45 or less.

[0044] In a specific example, in the incremental graph, the value of the minimum point between the first maximum point and the second maximum point may be 15% to 90% of the value of the first maximum point.

[0045] In a specific example, the porous carbon body may be a porous carbon body doped with a different element.

[0046] According to one disclosure, a catalyst for a fuel cell includes the above porous carbon body and a catalyst substance supported on the porous carbon body.

[0047] According to one disclosure, a catalyst layer for a fuel cell includes the above catalyst and an ionomer.

[0048] The present invention includes a polymer electrolyte membrane fuel cell including the above catalyst.

[0049]

Advantages of the Invention

[0050] According to one disclosure, the porous carbon body has an inherent pore structure, and thus, when used as a catalyst support for a fuel cell, it can exhibit improved mass activity.

[0051] Due to the inherent pore structure, in a specific example of the porous carbon body, both reactants and products of the fuel cell can have smooth mass transfer, and further, hydrogen ions can also move smoothly. Thus, when used as a catalyst support for a fuel cell, it can exhibit improved mass activity.

[0052] According to another specific example, the porous carbon body has an improved mass activity due to its inherent pore structure and has high crystallinity. Thus, when used as a catalyst support for a fuel cell, it can exhibit improved durability.

[0053] The various and beneficial advantages and effects of the present invention are not limited to the above, and will be more easily understood in the process of explaining specific examples of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 is a figure showing an increment graph of a porous carbon body manufactured according to an embodiment.

[0055] Figure 2 and Figure 3 is a figure showing an increment graph of a comparative sample. Detailed Description

[0056] The terms used in this specification are intended to describe the present invention and are not intended to limit the present invention. Further, unless the relevant definition clearly indicates the contrary meaning, the singular forms used in this specification also include the plural forms.

[0057] The meaning of "comprising" used in the specification is intended to specify the components, rather than excluding the existence or addition of other components.

[0058] Unless otherwise defined, all terms, including technical terms and scientific terms, used in this specification have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Terms defined in advance are interpreted to have meanings consistent with the relevant technical literature and the presently disclosed content.

[0059] In this specification and the appended claims, terms such as first, second, etc. do not have a limiting meaning, but are intended to be used to distinguish one component from another.

[0060] In this specification and the appended claims, fuel cells may include polymer electrolyte membrane fuel cells (PEMFCs), phosphate fuel cells (PAFCs), alkaline fuel cells (AFCs), molten carbonate fuel cells (MCFCs), or solid oxide fuel cells (SOFCs), etc. However, according to a specific example, the porous carbon body can exhibit improved mass activity when loading catalyst substances, so expensive catalyst substances can be more effectively utilized in commonly used fuel cells. As an example of such a fuel cell, polymer electrolyte membrane fuel cells (PEMFCs) or phosphate fuel cells (PAFCs), etc. can be cited.

[0061] In this specification and the appended claims, the classification of pore sizes is based on the definition of the International Union of Pure and Applied Chemistry (IUPAC). Specifically, according to the IUPAC definition, micropores refer to pores with a diameter of 2 nm or less, mesopores refer to pores with a diameter of 2 nm to 50 nm, and macropores refer to pores with a diameter of 50 nm or more.

[0062] In this specification and the appended claims, the nitrogen adsorption / desorption isotherm refers to an isotherm that combines the isotherm of the nitrogen adsorption process (nitrogen adsorption isotherm) obtained from the nitrogen adsorption measurement of a porous carbon body and the isotherm of the nitrogen desorption process (nitrogen desorption isotherm). Illustrated in detail by a graph with the x-axis of the relative pressure of nitrogen P / P0 and the y-axis of the nitrogen adsorption amount (cm 3 / g STP), the nitrogen adsorption / desorption isotherm has the same x-axis and the same y-axis, and refers to a graph that shows the nitrogen adsorption isotherm and the nitrogen desorption isotherm together. The hysteresis loop can refer to the form in which the nitrogen adsorption isotherm and the nitrogen desorption isotherm in the nitrogen adsorption / desorption isotherm are separated from each other. In other words, the hysteresis loop can refer to a certain region where the nitrogen adsorption amount shows different values at the same relative pressure due to the difference between the nitrogen adsorption process and the nitrogen desorption process.

[0063] The present inventors have conducted research on a porous carbon body material for a fuel cell catalyst support that is known in a trade-off relationship to satisfy high porosity and high crystallinity. During the continuation of this research, it was found that a coarser pore structure including mesopores and macropores of a porous carbon body for a fuel cell catalyst support has a great influence on the mass activity of a fuel cell catalyst substance. Based on such a finding, as a result of in-depth research, a porous carbon body pore structure that can greatly improve the mass activity of a catalyst substance was established, thus completing the present invention.

[0064] Based on the above findings, a disclosed porous carbon body satisfies the following Physical Property 1, Physical Property 2, and Physical Property 3:

[0065] Physical Property 1: The surface area of pores with a size of 2 nm or more and 5 nm or less obtained from the nitrogen desorption isotherm (N2 desorption isotherm) based on the BJH (Barrett-Joyner-Halenda) method based on the Harkins-Jura formula is 100 m 2 / g to 500 m 2 / g,

[0066] Physical Property 2: The surface area of pores with a size of 2 nm or more and 100 nm or less obtained from the nitrogen desorption isotherm (N2 desorption isotherm) based on the BJH (Barrett-Joyner-Halenda) method based on the Harkins-Jura formula is 200 m 2 / g to 1500 m 2 / g,

[0067] Physical property 3: The nitrogen adsorption / desorption isotherm has a hysteresis loop, and in the relative pressure range of 0.3 to 1.0, the graph of the value obtained by subtracting the value of the nitrogen adsorption isotherm from the value of the nitrogen desorption isotherm according to the relative pressure, that is, the incremental graph has at least a first maximum point and a second maximum point, and the value of the first maximum point at the lower relative pressure is less than the value of the second maximum point at the higher relative pressure.

[0068] The pore region with a size of 2 nm or more and 5 nm or less is the region that mainly affects the loading of the catalyst substance. According to the specific surface area of the pore region with a size of 2 nm to 5 nm, the characteristics of the catalyst substance loaded on the porous carbon body can be determined.

[0069] Since the porous carbon body satisfies Physical property 1, the catalyst substance can be loaded on the porous carbon body in the form of extremely fine particles with a size of several nanometers (for example, 1 to 3 nm), and the aggregation of the catalyst substance can be inhibited, thereby improving the stability and durability of the catalyst.

[0070] According to a specific example of the porous carbon body, the surface area of the pores with a size of 2 nm or more and 5 nm or less obtained from the nitrogen desorption isotherm by the BJH (Barrett-Joyner-Halenda) method based on the Harkins-Jura formula can satisfy 100 m 2 / g to 500 m 2 / g, specifically, it can satisfy 100 m 2 / g to 400 m 2 / g, more specifically, it can satisfy 100 m 2 / g to 350 m 2 / g.

[0071] The pore region with a size of 2 nm to 100 nm is the region that participates in the movement of reaction products of fuel cells such as water. Due to the specific surface area of the pore region with a size of 2 nm to 100 nm, the overall characteristics of the fuel cell may be affected. Since the porous carbon body satisfies Physical property 2, the reaction products of the fuel cell can move smoothly during the operation of the fuel cell.

[0072] According to a specific example of the porous carbon body, the surface area of the pores with a size of 2 nm or more and 100 nm or less obtained from the nitrogen desorption isotherm by the BJH (Barrett-Joyner-Halenda) method based on the Harkins-Jura formula can satisfy 200 m 2 / g to 1500 m 2 / g, specifically, it can satisfy 200 m2 / g to 1000 m 2 / g, more specifically, it can satisfy 200 m 2 / g to 800 m 2 / g, more specifically still, it can satisfy 200 m 2 / g to 700 m 2 / g.

[0073] While satisfying the above physical property 1 and physical property 2, the porous carbon body according to a specific example can also satisfy the following physical property 3.

[0074] Physical property 3: The nitrogen adsorption / desorption isotherm has a hysteresis loop, and in the relative pressure P / P0 range of 0.3 to 1.0, the graph obtained by subtracting the value of the nitrogen adsorption isotherm from the value of the nitrogen desorption isotherm according to the relative pressure, that is, the incremental graph has at least a first maximum point and a second maximum point, and the value of the first maximum point located at the lower relative pressure is less than the value of the second maximum point located at the higher relative pressure.

[0075] As is well known, the nitrogen adsorption / desorption isotherm represents the relationship between the nitrogen partial pressure and the nitrogen adsorption amount, and has an adsorption amount (cm 3 / g STP) value according to the relative pressure P / P0. The incremental graph is a graph obtained by subtracting the adsorption amount value of the nitrogen adsorption isotherm from the adsorption amount value of the nitrogen desorption isotherm (incremental value) according to the relative pressure type. Therefore, similar to the nitrogen adsorption / desorption isotherm, the incremental graph has a graph with the relative pressure P / P0 as the x-axis and the adsorption amount difference (incremental value) in cm 3 / g STP unit as the y-axis value.

[0076] In the incremental graph, the maximum point can correspond to the boundary point between the increasing region where the incremental value increases as the relative pressure increases and the decreasing region where the incremental value decreases as the relative pressure increases. At this time, it is natural that the increasing region and the decreasing region form continuous regions with the boundary point as the reference.

[0077] Physical property 3 is a physical property related to the coarse pore structure containing mesopores and macropores in the porous carbon body. In physical property 3, the incremental graph having at least two maximum points may mean that the porous carbon body has a pore structure in which at least two coarse pore groups with different size ranges are developed. At the same time, the physical property that the value of the second maximum point located at the higher relative pressure is larger than the value of the first maximum point, which is the maximum point located at the lower relative pressure, may mean that among the two well-developed coarse pore groups, the porous carbon body has a coarse pore group with a relatively larger size range, and the coarse pore group with the relatively larger size range has a more developed pore structure.

[0078] Since the porous carbon body satisfies Physical Property 3, gaseous reactants such as oxygen can be smoothly supplied into the porous carbon body, while also preventing a decrease in fuel cell performance caused by the flooding phenomenon of pore blockage due to reaction products such as water.

[0079] As described above, the increment graph can have a first increasing region and a first decreasing region with the first maximum point as a boundary point, and a second increasing region and a second decreasing region with the second maximum point as a boundary point.

[0080] In the increment graph, the first increasing region, the first decreasing region, the second increasing region, and the second decreasing region are sequentially located in the direction of increasing relative pressure and can be continuously distributed with each other at the same time. "Continuously distributed with each other" means that except for the end point of the increment graph where the relative pressure of the hysteresis loop closes, no intersection is formed between the increment graph and the x-axis.

[0081] The fact that the increment graph does not contact the x-axis except at the end point of the increment graph means that at least two well-developed, coarsely porous groups with different size ranges in the porous carbon body are connected (communicated) with each other.

[0082] Specifically, the minimum point belonging to the boundary point between the first decreasing region and the second increasing region, in other words, the value of the minimum point located between the first maximum point and the second maximum point can be a positive real number. Specifically, it can be 15% to 90% of the first maximum point value. More specifically, it can be 20% to 85% of the first maximum point value. On the increment graph, for the porous carbon body having the above minimum point value, due to other pores, the two coarsely porous groups can have a pore structure with good connectivity with each other, so that the movement of substances containing reactants and reaction products can be carried out more easily and actively. Therefore, the porous carbon body having the above minimum point can stably maintain the characteristics of the fuel cell in a wide humidity range from low humidity to high humidity when used as a fuel cell catalyst support.

[0083] In a specific example, the relative pressure P / P0 at the closing point of the hysteresis loop in the nitrogen adsorption / desorption isotherm can be 0.45 or less. Specifically, it can be 0.40 to 0.45. More specifically, it can be 0.40 to 0.43. The hysteresis loop closing in the region around a relative pressure of 0.4 indicates that the pores of the porous carbon body contain pores with a certain amount of bottleneck structure.

[0084] In a specific example, the porous carbon body can have an increment graph with the first maximum point in the range (region) where the relative pressure P / P0 is above 0.4 and below 0.9, and the second maximum point in the range (region) where the relative pressure P / P0 is above 0.9 and below 1.0.

[0085] When at least two well-developed large pores groups are referred to as the first large pores group (pores contributing to the formation of the first maximum point) and the second large pores group (pores contributing to the formation of the second maximum point), the positions of the respective maximum points can represent the size ranges of the pores contributing to the respective large pores groups.

[0086] The first maximum point is located in the range (region) where the relative pressure is 0.4 or more and less than 0.9, specifically, in the range (region) where the relative pressure is 0.45 to 0.80. This means that the first large pores group is formed by pores having a size somewhat larger than the granular catalyst loaded on the porous carbon body. Due to such a first large pores group, a smooth and rapid gas-phase supply to the granular catalyst and a smooth and rapid discharge of the liquid phase from the granular catalyst can be achieved, and flooding can be effectively prevented. Due to the smooth mass transfer between the gas phase and the liquid phase, a high mass activity in the high-current region can be ensured.

[0087] As a specific example of the gas phase, gases participating in the fuel cell electrochemical reaction such as oxygen, air, or hydrogen can be cited. As a specific example of the liquid phase, liquids including reaction products of the fuel cell electrochemical reaction such as water can be cited. However, the present invention is not limited to the specific substances of the gas phase and the liquid phase.

[0088] The second maximum point is located in the range (region) where the relative pressure is 0.9 or more and less than 1.0, specifically, in the range (region) where the relative pressure is 0.93 to 0.98. This means that the second large pores group is formed by large pores of 100 nm or more. Due to such a second large pores group, a strong bond between the ion-conducting medium such as the ionomer and the porous carbon body can be achieved, and at least a part of the ion-conducting medium can be easily introduced into the interior of the porous carbon body, and smooth ion transfer to the granular catalyst can be achieved. The strong bond with the ion-conducting medium and the smooth ion transfer characteristics can enable a high mass activity in the low-current and medium-current regions.

[0089] As a specific example of the ion, hydrogen ions participating in the fuel cell electrochemical reaction can be cited. However, the present invention is not limited to the specific ion species.

[0090] As described above, the porous carbon body has a pore structure with a first maximum point in the range of 0.4 or more and less than 0.9, specifically, in the range of 0.45 to 0.80, and a second maximum point in the range of 0.9 or more and less than 1.0, specifically, in the range of 0.93 to 0.98 on the incremental graph. Therefore, smooth transfer of the gas phase, liquid phase, and ions is made possible, and thus, when used as a fuel cell catalyst support, an improved mass activity can be ensured even in a wide current region covering the low-current, medium-current, and high-current regions.

[0091] Furthermore, due to the extremely small points having the above dimensions, the porous carbon body has a first group of large pores formed by pores larger in size than the granular catalyst, and a second group of large pores formed by pores with a size of 100 nm or more, and these two groups of large pores are well-connected to each other. Therefore, the three phases of gas, liquid, and ions can move more smoothly and quickly into and inside the porous carbon body and between its inner and outer parts.

[0092] In a specific example, the maximum point ratio (M1 / M2) obtained by dividing the first maximum point value (M1) by the second maximum point value (M2) on the increment graph can be from 0.10 to 0.95, specifically from 0.15 to 0.90. Since the porous carbon body has a pore structure that satisfies the above maximum point ratio, the granular catalyst material located in the pore region of the porous carbon body with pore sizes of 2 nm to 5 nm can uniformly and smoothly supply gas and ions. Also, together with Physical Property 1, Physical Property 2, and Physical Property 3, when the above maximum point ratio is satisfied, the supply of the gas and ions can be maximized.

[0093] In a specific example, in the nitrogen adsorption / desorption isotherm of the porous carbon body, the area ratio HA2 / HA1 obtained by dividing the hysteresis loop area HA2 in the relative pressure P / P0 range of 0.9 to 1.0 by the hysteresis loop area HA1 in the relative pressure P / P0 range of 0.4 to 0.9 can be from 0.1 to 2.0, specifically from 0.1 to 1.5, and more specifically from 0.10 to 1.3.

[0094] The hysteresis loop area HA1 in the relative pressure range of 0.4 to 0.9 can represent the degree of development of the pores contributing to the first group of large pores, and the hysteresis loop area HA2 in the relative pressure range of 0.9 to 1.0 can represent the degree of development of the pores contributing to the second group of large pores.

[0095] The above area ratio HA2 / HA1 can indicate that the first group of large pores is formed by pores with a wide size range, and at the same time, the pores with a wide size range can be uniformly and well-developed.

[0096] Together with Physical Property 1, Physical Property 2, and Physical Property 3, the pore structure that satisfies the above area ratio can particularly enable the liquid phase movement inside the porous carbon body and the liquid phase discharge from the inside to the outside to proceed smoothly and quickly.

[0097] In a specific example, the porous carbon body can be an aggregate formed by random aggregation of primary particles, and the primary particles can include hollow particles. Therefore, the pore structure of the above porous carbon body can be formed by the pores within the primary particles themselves, between the primary particles, between the parts of the aggregate and the primary particles, between the parts of the aggregate and other parts of the aggregate, and between the aggregates.

[0098] The average primary particle size of the porous carbon body can be from 10 nm to 30 nm. At this time, the average primary particle size can be measured according to the ASTM D3849 standard. The D of the porous carbon body 50 can be from 0.5 μm to 2.0 μm. At this time, D 50 can represent the size corresponding to 50% in the mass cumulative particle size distribution of the porous carbon body. The D of the porous carbon body 50 can be obtained by measuring the particle size distribution with a laser diffraction particle size distribution measuring device after subjecting the dispersion liquid in which the porous carbon body is dispersed in a dispersion medium to ultrasonic treatment for 30 minutes.

[0099] In a specific example, the porous carbon body can also satisfy the following physical property 4:

[0100] Physical property 4: The average interlayer spacing d measured by X-ray diffraction method 002 is from 0.335 nm to 0.350 nm.

[0101] (002) plane average interlayer spacing d 002 is an index directly indicating the crystallinity of the carbon body forming the porous carbon body. It can represent d from 0.335 nm to 0.350 nm 002 is formed by a highly controllable, well-developed, and excellent crystalline carbon body framework with a coarse and large pore structure that satisfies physical property 1, physical property 2, and physical property 3.

[0102] Due to the excellent crystallinity of the carbon body framework, the porous carbon body can have more excellent oxidation resistance. Therefore, when the porous carbon body is used as a fuel cell catalyst support, the catalyst can have improved durability.

[0103] Meanwhile, or independently thereof, the porous carbon body can also satisfy the following physical property 5.

[0104] Physical property 5: The lattice constant L in the a-axis direction measured by X-ray diffraction method a is from 4 nm to 12 nm, specifically from 6 nm to 12 nm, more specifically from 7 nm to 12 nm, and even more specifically from 7.5 nm to 12 nm.

[0105] Physical property 5 is also related to the crystallinity of the porous carbon body. A larger L a value indicates that the carbon body framework of the porous carbon body is formed by graphite with a larger hexagonal mesh plane. Since the porous carbon body satisfies physical property 5, it is beneficial for reducing the defect sites vulnerable to oxidation.

[0106] Meanwhile, or independently thereof, the porous carbon body can also satisfy the following physical property 6.

[0107] Physical property 6: The average number of graphene layers calculated by X-ray diffraction is from 6 to 20, specifically from 7 to 15, and more specifically from 8 to 15.

[0108] Physical property 6 is also related to the crystallinity of the porous carbon body. The average number of graphene layers is the value calculated by adding 1 to the value obtained by dividing the lattice constant L c by d 002 . The larger the average number of graphene layers, the thicker the graphite crystals that form the carbon body framework of the porous carbon body.

[0109] In a favorable example, together with the above pore structure, the porous carbon body can have excellent crystallinity that fully satisfies physical properties 4, 5, and 6. When the porous carbon body has the above pore structure and crystallinity that fully satisfies physical properties 4, 5, and 6, in the thermogravimetric analysis (TGA) of the porous carbon body support, it can have a mass loss rate of 0% to 30% at 500°C to 700°C, specifically, at the level of 2% to 28%, or 10% to 28%, or 15% to 25%, or 18% to 20%, or 21% to 23%, showing excellent antioxidant properties.

[0110] In addition, when the porous carbon body has the above pore structure and crystallinity that fully satisfies physical properties 4, 5, and 6, in the thermogravimetric analysis of the porous carbon body support, the temperature at which the mass is reduced by 30% based on the raw material can show a high temperature of 700°C to 740°C, specifically, a high temperature of 705°C to 730°C, or 710°C to 715°C, or 715°C to 725°C, showing antioxidant properties. Experimentally, the thermogravimetric analysis of the porous carbon body can be measured by ASTM E1131.

[0111] In a specific example, the porous carbon body may be in a state doped with a foreign element. The foreign element may include one or more elements selected from metalloids, non-metals (excluding the carbon body), and transition metals. The metalloids may include one or more elements selected from boron, silicon, germanium, arsenic, antimony, tellurium, and polonium, and the non-metals may include one or more elements selected from nitrogen, oxygen, phosphorus, sulfur, and selenium. The transition metals are metals belonging to Groups 3 to 12. Specifically, they may include metals belonging to the 4th to 5th periods in Groups 3 to 12 (such as cobalt, iron, nickel, copper, zinc, chromium, vanadium, titanium, scandium, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, cadmium) and metals belonging to the lanthanide series (lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium). When the porous carbon body is doped with a foreign element, the porous carbon body may include 0.05% by mass to 5.00% by mass of the foreign element. Specifically, the porous carbon body may include 0.05% by mass to 5.00% by mass of the metalloid, 0.05 to 0.50% by mass of the non-metal, and / or 0.05% by mass to 2.00% by mass of the transition metal. Due to the doping of the foreign element, when used as a catalyst support for a fuel cell, the catalytic performance can be improved.

[0112] The present invention includes a catalyst for a fuel cell containing the above porous carbon body.

[0113] According to one aspect, a catalyst for a fuel cell includes a support including the above porous carbon body; and a catalyst substance supported on the support.

[0114] The catalyst substance may include known platinum-based catalysts, non-platinum-based catalysts, or mixtures thereof that catalyze the oxidation reaction (for example, oxidation of hydrogen) or reduction reaction (for example, reduction of oxygen) occurring in a fuel cell. As representative examples of platinum-based catalysts, platinum catalysts, alloy catalysts between platinum and noble metals (such as gold, silver, palladium, ruthenium, rhodium, iridium, osmium, etc.), alloy catalysts between platinum and non-noble metals (such as nickel, iron, cobalt, chromium, copper, manganese, vanadium, titanium, tantalum, niobium, magnesium, tin, bismuth, lead, aluminum, molybdenum, niobium, tantalum, zirconium, ruthenium, selenium, etc.), alloy catalysts between platinum, noble metals, and non-noble metals, composite catalysts of platinum-based metals and metal oxides, core-shell catalysts with a transition metal core and a platinum shell, etc. can be cited. As representative examples of non-platinum-based catalysts, non-platinum-based alloy catalysts such as ruthenium-iridium alloys or palladium-transition metal alloys, transition metal (such as nickel, iron, etc.)-N-based catalysts, transition metal (such as nickel, iron, etc.)-N-C-based catalysts, etc. can be cited. However, the above porous carbon body provides a pore structure that is more effective for the loading of catalyst substances having a size on the order of clusters or several nanometers, and thus is more advantageous for the loading of platinum-based catalysts.

[0115] The catalyst substance supported on the porous carbon body can be in the form of nanoparticles and, as a specific example, can have a size in the range of 0.5 nm to 4 nm.

[0116] The catalyst can contain 5 wt% to 70 wt% of the catalyst substance, specifically, it can be 10 wt% to 60 wt%, but the loading amount of the catalyst substance of the present invention is not limited thereto.

[0117] The present invention includes a catalyst layer for a fuel cell containing the above-mentioned porous carbon body.

[0118] According to one disclosure, a catalyst layer for a fuel cell can include the above-mentioned porous carbon body, a catalyst substance supported on the porous carbon body, and an ionomer.

[0119] The present invention includes a catalyst layer for a fuel cell containing the above-mentioned porous carbon body.

[0120] According to one disclosure, a catalyst layer for a fuel cell can include the above-mentioned catalyst and an ionomer.

[0121] The ionomer may be any known polymeric substance that conducts ions participating in the fuel cell reaction. As a specific example, the ionomer can be a proton-conductive ionomer. As an example of a proton-conductive ionomer, known sulfonated block copolymers, perfluoropolymers having sulfonic acid groups in the side chains, or sulfonated aromatic polymers, etc. can be cited. It is also possible to use commercial products as the ionomer. As an example of such commercial products, (DuPont), (Asahi Kasei Corporation), and (Asahi Glass Co., Ltd.) etc.

[0122] The content of the above-mentioned catalyst in the catalyst layer is not limited as long as it can stably achieve the target catalytic performance during the electrochemical reaction of the fuel cell and as long as it is the amount of catalyst typically contained in a fuel cell catalyst layer. As a practical example, the catalyst layer can include 10 wt% to 90 wt% of the above-mentioned catalyst, specifically, it can include 30 wt% to 90 wt%, but the present invention is not limited to the specific catalyst content in the catalyst layer.

[0123] If necessary, together with the above-mentioned catalyst and ionomer, the catalyst layer can further include a carbon material. The carbon material can include the above-mentioned porous carbon body without introducing a catalyst substance, particulate conductive carbon materials, carbon materials with one-dimensional nanostructures (for example, carbon nanotubes or carbon fibers, etc.), carbon materials with two-dimensional nanostructures (for example, graphene, reduced graphene oxide, graphene oxide, etc.), or mixtures thereof, etc.

[0124] The present invention includes a membrane-electrode assembly comprising the above-described catalyst layer.

[0125] According to one disclosure, a membrane-electrode assembly may include an anode, a cathode, and an electrolyte membrane disposed between the anode and the cathode. The anode may include a first gas diffusion layer and a first catalyst layer, and the cathode may include a second gas diffusion layer and a second catalyst layer. At this time, the first catalyst layer of the anode and the second catalyst layer of the cathode may be distributed to contact the electrolyte membrane.

[0126] At least one of the first catalyst layer and the second catalyst layer may include the above-described porous carbon body or the above-described catalyst. In fact, at least one of the first catalyst layer and the second catalyst layer may be the above-described catalyst layer for a fuel cell.

[0127] If necessary, in the anode or the cathode, a microporous layer or the like for improving the hydrophobic property may be further provided between the gas diffusion layer and the catalyst layer, but the present invention is not limited to the specific structure of the membrane-electrode assembly.

[0128] The gas diffusion layer may be any substance commonly used in the field of fuel cells. As a representative example of the gas diffusion layer, polyethylene terephthalate having a hydrophobic property, carbon paper, etc. can be cited, but it is not limited thereto.

[0129] The electrolyte membrane may also be any well-known membrane commonly used for target ion conduction in the field of fuel cells. As an example, the electrolyte membrane may be a hydrogen ion conductive electrolyte membrane. As a representative example of the hydrogen ion conductive electrolyte membrane, sulfonated block copolymers, perfluoropolymers having sulfonic acid groups on the side chains, or sulfonated aromatic polymers, etc. can be cited. As a representative example of commercial products, (DuPont), (Asahi Kasei Corporation), and (Asahi Glass Co., Ltd.) etc.

[0130] The present invention includes a fuel cell comprising the above-described porous carbon body, the above-described catalyst, the above-described catalyst layer, or the above-described membrane-electrode assembly.

[0131] The present invention includes a fuel cell stack in which the above-described membrane-electrode assembly is used as a unit cell and a plurality of unit cells are stacked. At this time, each stacked unit cell may be located between separators formed with flow paths.

[0132] The present invention includes a method for manufacturing the above-described porous carbon body.

[0133] The manufacturing method of a porous carbon body according to a specific example may include: S1) a step of heat-treating a carbon raw material at 1000°C to 3000°C to remove impurities and crystallize; S2) a step of pre-treating the carbon raw material that has been de-impurized and crystallized in an atmosphere containing at least one foreign element selected from the group consisting of boron, carbon, nitrogen, oxygen, phosphorus, and sulfur to introduce active sites doped with foreign elements; S3) a step of mixing an additive containing an organic surfactant into the carbon raw material into which the active sites have been introduced, and then heat-treating to remove the foreign elements to activate the carbon raw material; S4) a step of washing the activated carbon raw material and then drying; S5) a step of performing secondary crystallization treatment on the activated carbon raw material after washing and drying; S6) a step of pre-treating the carbon raw material that has been subjected to secondary crystallization treatment in an atmosphere containing at least one second foreign element selected from the group consisting of boron, carbon, nitrogen, oxygen, phosphorus, and sulfur to introduce secondary active sites into the carbon raw material; S7) a step of mixing an additive containing a second organic surfactant into the carbon raw material into which the second active sites have been introduced and performing heat treatment for secondary activation treatment; and S8) a step of washing the raw material after secondary activation treatment and then drying.

[0134] Steps S1) to S4) are processes mainly aimed at making the mesopores with a size of several nanometers or less developed while improving the crystallinity of the carbon raw material; steps S5) to S8) may be processes for making the coarser macropores containing mesopores and macropores more developed, thereby establishing the target pore structure.

[0135] Specifically, after highly crystallizing the carbon raw material through step S1), in step S2), foreign elements can be inserted into the carbon molecular structure to form unstable sites (sites with relatively high energy) in the carbon with a high crystalline phase. During the activation step S3), the unstable sites formed in the highly crystallized carbon structure can induce a higher frequency of activation reactions to improve crystallinity and yield. At the same time, the unstable sites act as sites for pore formation, and thus an intermediate product that simultaneously satisfies the good development of mesopores with a size of several nanometers or less and high crystallinity can be manufactured.

[0136] After that, the intermediate product that simultaneously satisfies high porosity and high crystallinity is subjected to re-crystallization treatment, and then due to the introduction of unstable sites of foreign elements, during the secondary activation treatment, it develops into mesopores and macropores, and thus has the target pore structure, and a porous carbon body with excellent crystallinity can be manufactured.

[0137] Specifically, step S1) is a process of heat-treating the carbon raw material to remove impurities and crystallize it. As a result, in step S2), foreign elements can effectively penetrate into the interior of the carbon raw material. Herein, "impurities" refer to substances other than carbon present on the surface or inside of the carbon raw material. As an example based on substances, it may include petroleum residues, other functional groups, etc., and as an example based on elements, it may include elements other than carbon (boron, carbon, nitrogen, oxygen, phosphorus, sulfur, etc.), but is not limited thereto. In step S1), as the lattice constant of the carbon raw material increases, part or all of the raw material may crystallize.

[0138] In a specific example, the carbon raw material can be amorphous carbon such as hard carbon like cellulose, phenolic resin, isotropic pitch, etc., and soft carbon like mesophase pitch, needle coke, etc.; it can also be crystalline carbon such as artificial graphite, natural graphite, etc.; more specifically, it can be soft carbon. Soft carbon exhibits relative anisotropy compared to hard carbon, and the carbon layer planes are arranged parallel to each other and can be crystallized through heat treatment at 1000 °C or higher, that is, graphitization can be performed. Depending on the situation, the carbon raw material may include carbon nanotubes (CNT), carbon nanofibers (CNF), etc.

[0139] Step S1) can be carried out in a vacuum or an inert gas (such as nitrogen, argon, neon, helium, etc.) atmosphere at a temperature of 1000 °C to 3000 °C for 10 minutes or more. Such conditions are for removing impurities other than carbon present in the carbon raw material while performing carbon crystallization. Specifically, step S1) can be carried out in a vacuum or an inert gas atmosphere at a temperature of 1000 °C to 2000 °C, and more specifically, at a temperature of 1000 °C to 1800 °C, for 10 minutes to 100 minutes.

[0140] Step S2) is a process of introducing a predetermined foreign element into the carbon raw material that has been purified of impurities and crystallized. In this process, the carbon raw material can be selectively replaced by the foreign element from the parts with low crystallinity inside. The introduction point of the foreign element becomes the starting point of the reaction in the subsequent activation process, and thus can serve as a site for micropore formation.

[0141] The pretreatment of step S2) can be carried out by heat treatment in an atmosphere containing at least one foreign element selected from the group consisting of boron, carbon, nitrogen, oxygen, phosphorus, and sulfur supplied at 100 sccm to 600 sccm at 500 °C to 1000 °C for 30 minutes to 100 minutes. Under an atmosphere supplying a large amount of foreign elements, by performing the pretreatment at a relatively low temperature and for a short time, the foreign element can be introduced more selectively into the low-crystallinity parts.

[0142] As a practical example, the hetero element may be at least one selected from the group consisting of boron, carbon, nitrogen, oxygen, phosphorus, and sulfur.

[0143] Step S3) is a process of formally forming micropores by using the hetero element inserted in the pretreatment step as a reaction starting point. Due to the reaction between the hetero element and the additive in step S3), a developed microporous structure mainly composed of mesopores with a micropore size of several nanometers can be formed. While the partially doped hetero element with weak crystallinity is removed during the activation process, the crystallinity is improved, and at the same time, air holes can be formed. Finally, an intermediate product showing both a highly porous structure and high crystallinity can be manufactured.

[0144] Based on 100 parts by weight of the carbon raw material introducing activation sites, the mixture of the carbon raw material introducing activation sites and the additive may include 0.1 to 10 parts by weight of an inorganic or organic surfactant, 0.1 to 10 parts by weight of an alkali metal hydroxide, and 1 to 10 parts by weight of neutral water. Specifically, based on 100 parts by weight of the carbon raw material introducing activation sites, the mixture may contain 0.5 to 5 parts by weight of an organic surfactant, 0.5 to 5 parts by weight of an alkali metal hydroxide, and 1 to 8 parts by weight of neutral water.

[0145] The alkali metal hydroxide may be one or more selected from the group consisting of lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide, but is not limited thereto. The organic surfactant may be at least any one selected from sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, lithium dodecyl sulfate, cetyltrimethylammonium bromide, dodecyltrimethylammonium bromide, polyvinylpyrrolidone, Triton X series, Brij series, Tween series, poly(acrylic acid), and polyvinyl alcohol, but is not limited thereto.

[0146] The heat treatment in step S3) can be carried out in an inert gas atmosphere at 500 °C to 1000 °C for 10 minutes to 100 minutes. Specifically, it can be carried out at 600 °C to 900 °C for 10 minutes to 600 minutes.

[0147] Step S_{4}) is a step of drying the activated carbon raw material obtained by washing in step S3). The washing can be carried out using an acid, a base, water, etc. to make the pH value of the aqueous dispersion of the carbon raw material reach 5 to 9. Specifically, it can be carried out until the pH is 6 to 8. The drying can be carried out at a temperature of 70 °C to 120 °C and atmospheric pressure conditions for 10 to 20 hours, and then at a temperature of 80 °C to 150 °C and vacuum conditions for 1 hour to 5 hours, but is not limited thereto. The drying conditions in step S_{4}) may be carried out as long as they can sufficiently remove the water in the carbon body (intermediate product).

[0148] The secondary crystallization in step S5) can be carried out in a vacuum or an inert gas (nitrogen, argon, neon, helium, etc.) atmosphere at 1000 °C to 1500 °C for 10 minutes to 60 minutes. Specifically, step S1) can be carried out in a vacuum or an inert gas atmosphere at 1000 °C to 1200 °C for 10 minutes to 50 minutes.

[0149] The secondary pretreatment in step S6) can be carried out by heat treatment at 500 °C to 1000 °C for 60 minutes to 500 minutes in an atmosphere supplied at 100 sccm to 600 sccm and containing at least one foreign element selected from the group consisting of boron, carbon, nitrogen, oxygen, phosphorus, and sulfur. When introducing a secondary foreign element, heat treatment can be carried out for a relatively long time at a relatively low temperature in an atmosphere supplied with a large amount of the foreign element.

[0150] As a practical example, the foreign element can be at least one selected from the group consisting of boron, carbon, nitrogen, oxygen, phosphorus, and sulfur.

[0151] Step S7), i.e., the secondary activation treatment step, can be a step of growing the pores introduced through steps S2) to S3) and generating new pores to develop mesopores to macropores. Through step 6), based on 100 parts by weight of the carbon raw material introducing the secondary activation sites, the mixture of the carbon raw material introducing the secondary activation sites and the additive can contain 0.1 part by weight to 10 parts by weight of an inorganic or organic surfactant, 0.1 part by weight to 10 parts by weight of an alkali metal hydroxide, and 1 part by weight to 10 parts by weight of neutral water. Specifically, based on 100 parts by weight of the carbon raw material introducing the secondary activation sites, the mixture can include 0.5 part by weight to 5 parts by weight of an organic surfactant, 0.5 part by weight to 5 parts by weight of an alkali metal hydroxide, and 1 part by weight to 8 parts by weight of neutral water. During the secondary activation treatment, heat treatment can be carried out for a relatively long time at a relatively high temperature.

[0152] The alkali metal hydroxide can be selected from one or more of the group consisting of lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide, but is not limited thereto. The organic surfactant can be selected from at least any one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, lithium dodecyl sulfate, cetyltrimethylammonium bromide, dodecyltrimethylammonium bromide, polyvinylpyrrolidone, Triton X series, Brij series, Tween series, poly(acrylic acid), and polyvinyl alcohol, but is not limited thereto.

[0153] During the secondary activation in step S7), the heat treatment can be carried out in an inert gas atmosphere at 500 to 1000 °C for 10 minutes to 300 minutes. Specifically, it can be carried out at 650 °C to 850 °C for 30 minutes to 250 minutes.

[0154] The cleaning and drying in step S8) may be performed substantially in the same manner as in step S4).

[0155] (Example 1)

[0156] The carbon raw material (Li-435, Denka Company Limited) was heated at 1000 °C for 30 minutes in an argon atmosphere for crystallization treatment. Thereafter, a mixed gas of oxygen and nitrogen (in the gas, 50 vol% oxygen and 50 vol% nitrogen) was introduced into the crystallized carbon raw material at a flow rate of 300 sccm, and heat treatment was performed at a temperature of 600 °C for 1 hour to carry out the activated site introduction process. Thereafter, for 100 parts by weight of the carbon raw material into which the activated sites were introduced, an organic surfactant, potassium hydroxide, and water were added to the carbon raw material into which the activated sites were introduced, and after stirring for 60 minutes, drying was performed with hot air to produce a mixture such that the organic surfactant (Triton X-100) was 1 part by weight, potassium hydroxide was 1 part by weight, and neutral water was 3 parts by weight. Thereafter, the produced mixture was heat-treated (activation treatment) at a temperature of 700 °C for 30 minutes in a nitrogen atmosphere. Hydrochloric acid, ammonia water, and neutral water were sequentially added to the sample after the activation treatment, and after stirring for more than 30 minutes each, vacuum filtration was performed for cleaning. During cleaning, the processes of hydrochloric acid and ammonia water were each performed once, and the amount added was such that the hydrochloric acid was 1 times the weight of the previously used potassium hydroxide, and the amount added was such that the ammonia water was 1 times the weight of the previously used hydrochloric acid. The process of cleaning with neutral water was repeated until the pH value of the solution during stirring reached the range of 6 to 8. Finally, when the pH reached the target, drying was performed at a temperature of 120 °C and atmospheric pressure for more than 12 hours, and thereafter, additional drying was performed at a temperature of 120 °C and under vacuum conditions for more than 1 hour.

[0157] After additional drying, the recovered carbon body was heated at 1000 °C for 30 minutes in an argon atmosphere for secondary crystallization treatment. Thereafter, a mixed gas of oxygen and nitrogen (in the gas, 50 vol% oxygen and 50 vol% nitrogen) was introduced into the carbon raw material after the secondary crystallization treatment at a flow rate of 300 sccm, and heat treatment was performed at a temperature of 600 °C for 1 hour to carry out the secondary activation site introduction process. Thereafter, for 100 parts by weight of the carbon raw material into which the secondary activation site was introduced, an organic surfactant, potassium hydroxide, and water were added to the carbon raw material into which the activation site was introduced, and after stirring for 60 minutes, drying was performed with hot air to produce a secondary mixture such that the organic surfactant (Triton X-100) was 1 part by weight, potassium hydroxide was 1 part by weight, and neutral water was 3 parts by weight. Thereafter, the produced secondary mixture was heat-treated (secondary activation treatment) at a temperature of 700 °C for 60 minutes in a nitrogen atmosphere. As described above, the sample after the secondary activation treatment was washed with hydrochloric acid, ammonia water, and neutral water and dried to produce a porous carbon body.

[0158] (Examples 2 to 4)

[0159] A porous carbon body was produced in the same manner as in Example 1, except that the secondary activation site introduction conditions and the secondary activation treatment conditions were carried out according to the conditions shown in Table 1 below.

[0160] (Table 1)

[0161]

[0162] The produced porous carbon body was analyzed according to the following conditions.

[0163] Measurement of nitrogen adsorption / desorption

[0164] The nitrogen adsorption / desorption isotherm can be obtained by measuring the change in the nitrogen adsorption amount of the porous carbon body according to the change in nitrogen pressure at a temperature of 77 K.

[0165] Experimentally, the nitrogen adsorption / desorption isotherm was measured based on ASTM D6556.

[0166] Specifically, in addition to ASTM D6556, the sample preparation for obtaining the nitrogen adsorption / desorption isotherm follows the steps below:

[0167] 1) Weigh 300 mg of the porous carbon body sample.

[0168] 2) Dry the sample at a vacuum of 0.1 Torr or less and 200 °C for 12 hours.

[0169] 3) Measure the nitrogen adsorption / desorption isotherm using a specific surface area measurement device (for example, Micromeritics, ASAP 2460).

[0170] In addition to ASTM D6556, the measurement conditions for obtaining the nitrogen adsorption / desorption isotherm are as follows:

[0171] For the nitrogen adsorption gas, use liquid nitrogen to achieve a temperature of 77K, a relative pressure P / P0 measurement precision of 0.02, and a relative pressure P / P0 range of 0 to 1.

[0172] BJH method based on Harkins-Jura formula

[0173] Using the BJH method, convert the relative pressure P / P0 of nitrogen in the adsorption / desorption isotherm to pore size (nm), and convert the nitrogen adsorption amount (cm 3 / g STP) to pore volume (cm 3 / g), thus obtaining the pore size distribution. At this time, when converting the relative pressure to pore size, use the Harkins and Jura thickness curve for correction. In addition, a flame atomic absorption spectrometry (Faas) correction with standard BJH correction was also performed together with the Harkins and Jura thickness curve. For the adsorption isotherm, the conversion between pore size and pore volume is carried out in the pore size range of 1.7 nm to 300 nm, and for the desorption isotherm, the conversion between pore size and pore volume is carried out in the pore size range of 2.0 nm to 50 nm.

[0174] X-ray diffraction measurement

[0175] The X-ray diffraction measurement of the porous carbon body applies the ASTM D5357 standard and is obtained under the following measurement conditions using a general X-ray diffraction measurement device (for example, RIGAKU, SmartLab SE):

[0176] 0.5 g of porous carbon body powder, Cu Kα line, a scanning range of 10 to 70°, a scanning speed of 5.0° / min, and a scanning step of 0.03°.

[0177] d of the X-ray diffraction pattern of the porous carbon body 002 、L a 、L c

[0178] d 002 is the average layer spacing (nm) of the porous carbon body based on the (002) plane, calculated according to Bragg's law (d 002 = λ / 2sinθ 002 , where λ = X-ray wavelength (nm)).

[0179] The crystallite height (L c , nm) and crystallite length (L a , nm) of the specified grain size in the porous carbon body are calculated by the following Scherrer formula.

[0180] Grain size (nm) = (k·λ) / (β0·cosθ)

[0181] For L a , k (shape factor) = 1.84, β0 = full width at half maximum (radian) of the (100) peak in the X-ray diffraction pattern of the porous carbon body, λ = X-ray wavelength (nm), θ = diffraction angle (Bragg angle, radian) of (100).

[0182] For L c , k (shape factor) = 0.9, β0 = full width at half maximum (radian) of the (002) peak in the X-ray diffraction pattern of the porous carbon body, λ = X-ray wavelength (nm), θ = diffraction angle (Bragg angle, radian) of (002).

[0183] Under the following conditions, a catalyst, a catalyst-coated film, and a single cell are manufactured using the manufactured porous carbon body, and their electrochemical properties are analyzed.

[0184] Manufacture of catalyst

[0185] After dispersing 0.75 g of the porous carbon body in a mixture of 388.2 g of ethylene glycol (EG) and water (water:EG weight ratio = 1:1) to prepare a dispersion, 4.95 g of a 20 wt% aqueous solution of a platinum precursor is added to the prepared dispersion to prepare a mixed solution. The prepared mixed solution is heated at 105 °C for 1 hour to load platinum particles onto the porous carbon body. Then, the mixed solution is cooled to room temperature, and the porous carbon body loaded with platinum particles is filtered out, washed thoroughly with distilled water, and dried in a vacuum dryer at a temperature of 250 °C to manufacture a catalyst.

[0186] Manufacture of catalyst coated membrane (CCM)

[0187] Using an active area of 25 cm 2Catalyst-coated membrane (CCM) preparation Membrane-electrode assemblies (MEAs). In all tests, commercial Pt / C (manufacturer: Nakada Precious Metals Co., product number: 1021-E941, Pt catalyst loading: 19.9%) was used as the oxidation electrode (anode) catalyst, and the catalyst manufactured in the examples was used as the active reduction electrode (cathode) catalyst. All catalyst slurries were prepared by mixing distilled water, Nafion (20 wt% in DI water + 1-propanol ratio 0.739), and 1-propanol into the catalyst. The manufactured catalyst slurry was coated on a fluorinated polyimide film at a constant speed of 15 mm / second using a bar coater. The film was dried at 60 °C for 12 hours to manufacture the reduction electrode. The reduction electrode thus obtained was pressed together with a commercial oxidation electrode and a Nafion membrane at 145 °C for 15 minutes using a vacuum press to finally manufacture the catalyst-coated membrane.

[0188] Performance test

[0189] The performance of the proton exchange membrane fuel cell (PEMFC) was tested at 80 °C. For the high-humidity test, highly humidified (relative humidity 100%) high-purity hydrogen was supplied to the oxidation electrode, and fully humidified (relative humidity 100%) air was supplied to the reduction electrode. Additionally, for the low-humidity test, low-humidified (relative humidity 40%) high-purity hydrogen was supplied to the oxidation electrode, and low-humidified (relative humidity 40%) air was supplied to the reduction electrode. The minimum flow rate value of all high-purity hydrogen in the high-humidity test and the low-humidity test was 100 sccm, and the minimum flow rate value of air was 200 sccm. During the performance test, the stoichiometry ratio was set to H2 / Air = 1.5 / 1.8, and the back pressure was maintained at 1.5 bar.

[0190] Electrochemical impedance spectroscopy (EIS) was measured in the range of 0.1 kHz to 100 kHz at a voltage of 0.1 V RHE under the conditions of 500 sccm of low-humidified (relative humidity 40%) high-purity hydrogen and 500 sccm of low-humidified (relative humidity 40%) high-purity nitrogen. During the test, the back pressure was maintained at 1.5 bar.

[0191] For comparison with the porous carbon bodies fabricated in the examples, the crystallinity and pore characteristics of commercial carbon bodies were analyzed in the same manner as when analyzing the porous carbon bodies. Also, in the same way as for the porous carbon bodies, catalysts, catalyst-coated membranes, and single cells were fabricated using the commercial carbon bodies, and their electrochemical characteristics were evaluated. The commercial carbon bodies used for comparison were Li-250 (Denka Company Limited), Li-400 (Denka Company Limited), Li-435 (Denka Company Limited), MH-00 (CNovelTM, TOYO TANSO), MH-18 (CNovel TM , TOYO TANSO), and MH-18_2μm (CNovelTM, TOYO TANSO).

[0192] Hereinafter, when referring to the results measured using each commercial carbon body or the porous carbon bodies fabricated in the examples, only the specific product name of the commercial carbon body or the example number is used. For example, the electrochemical characteristics of a single cell fabricated using MH-18 (CNovel TM , TOYOTANSO) as the Pt support can be referred to as the electrochemical characteristics of MH-18. For example, the incremental plot derived from the nitrogen adsorption / desorption isotherm of MH-18 (CNovel TM , TOYO TANSO) can be referred to as the incremental plot of MH-18. For example, the porous carbon bodies fabricated in Example 1, the catalysts, catalyst-coated membranes, single cells fabricated using the porous carbon bodies as the Pt support, and the electrochemical characteristics of the single cells can be referred to as the porous carbon bodies of Example 1, the catalysts of Example 1, the catalyst-coated membranes of Example 1, the single cells of Example 1, and the electrochemical characteristics of Example 1.

[0193] The surface areas of 2 - 5 nm (SSA1, m 2 / g), 2 - 100 nm (SSA2, m 2 / g), d 002 (nm), L a (nm), and the average number of graphite layers (average number of layers, pieces) of the porous carbon bodies fabricated in the examples and the comparative samples were measured and tabulated in Table 2.

[0194] (Table 2)

[0195] SSA1 SSA2 <![CDATA[d 002 > <![CDATA[L a > Average number of layers Example 1 264.82 395.68 0.350 8.31 9.45 Example 2 222.76 423.03 0.350 9.05 9.57 Example 3 295.03 520.90 0.350 9.04 9.42 Example 4 178.89 266.43 0.350 7.97 9.27 Li-250 23.22 45.86 0.350 8.15 8.65 Li-400 18.13 35.30 0.353 7.52 7.94 Li-435 60.91 121.08 0.351 8.24 8.78 MH-00 1317.11 1622.43 0.362 3.96 3.07 MH-18 1027.47 1255.75 0.345 7.49 17.00 MH-18_2μm 1066.94 1305.47 0.342 7.58 11.49

[0196] Figure 1 is a figure showing the incremental plot of the porous carbon body of Example 1. The incremental plots of the comparative samples are also illustrated as Figure 2 (the incremental plot of the Li-400 sample) andFigure 3 (Incremental graph of MH-18 sample).

[0197] The porous carbon body manufactured in the examples has a hysteresis loop in the nitrogen adsorption / desorption curve, as Figure 1 shown, having a hysteresis loop that closes near a relative pressure of 0.4.

[0198] As Figure 1 shown, the porous carbon body manufactured in the examples has two peak values on the incremental graph, and the size of the peak value (the second peak value) located at a higher relative pressure is larger than the size of the peak value (the first peak value) located at a lower relative pressure.

[0199] The number of maximum points, the first maximum point value (cm 3 / g STD), the second maximum point value (cm 3 / g STD), and the ratio of the maximum point values (the first maximum point value / the second maximum point value) on the incremental graphs of the porous carbon body manufactured in the examples and the comparative samples are tabulated in Table 3.

[0200] (Table 3)

[0201] Number of maximum points Value of the first maximum point Value of the second maximum point Ratio of maximum point values Example 1 2 21.55 27.83 0.77 Example 2 2 35.47 49.53 0.72 Example 3 2 34.76 102.36 0.34 Example 4 2 6.02 38.57 0.16 Li-250 1 9.52 - - Li-400 1 7.32 - - Li-435 1 25.50 - - MH-00 2 129.08 88.41 1.46 MH-18 2 129.04 83.82 1.54 MH-18_2μm 2 110.69 18.05 6.13

[0202] The first maximum point position (P / P0), the second maximum point position (P / P0), and the minimum point size between the first maximum point and the second maximum point (expressed as a percentage of the first maximum point value based on the first maximum point value) on the incremental graphs of the porous carbon body manufactured in the examples and the comparative samples are tabulated in Table 4.

[0203] (Table 4)

[0204]

[0205]

[0206] In the nitrogen adsorption / desorption isotherms of the porous carbon body manufactured in the examples and the comparative samples, the hysteresis loop area HA1 in the range of relative pressure from 0.4 to 0.9 and the hysteresis loop area HA2 in the range of relative pressure from 0.9 to 1.0 are respectively obtained, and the area ratio HA2 / HA1 is calculated and tabulated in Table 5.

[0207] (Table 5)

[0208] HA1 HA2 HA2 / HA1 Example 1 7.33 1.13 0.15 Example 2 10.71 2.99 0.28 Example 3 10.81 6.41 0.59 Example 4 1.91 2.45 1.28 Li-250 0.14 0.49 3.42 Li-400 0.05 0.35 6.52 Li-435 0.67 1.58 2.37 MH-00 40.15 1.67 0.04 MH-18 40.66 1.60 0.04 MH-18_2μm 32.85 1.63 0.05

[0209] The electrochemical properties of the single cells fabricated using the porous carbon bodies produced in the usage examples and the carbon bodies of the comparative samples are tabulated in Table 6 (low humidification condition with 40% relative humidity) and Table 7 (high humidification condition with 100% relative humidity). In Tables 6 and 7, J@0.6V represents the current density measured at a fixed voltage of 0.6V, V@0.8A / cm 2 and V@1.5A / cm 2 represent the voltages measured at fixed current densities of 0.8A / cm 2 and 1.5A / cm 2 respectively. In Tables 6 and 7, "V ratio" is the ratio (in %) of the voltage measured under the low current density condition of 0.8A / cm 2 divided by the voltage measured under the high current density condition of 1.5A / cm 2 .

[0210] (Table 6)

[0211]

[0212] (Table 7)

[0213]

[0214] Regarding the analysis results of the electrochemical impedance spectra under the low humidification condition, the resistances of the reduction electrodes fabricated using the carbon bodies of Examples 1 - 4 are all 0.10Ω / cm 2 ; the resistances of both the Li - 250 reduction electrode and the Li - 400 reduction electrode are 0.15Ω / cm 2 ; the resistance of the Li - 435 reduction electrode is 0.13Ω / cm 2 ; the resistances of both the MH - 00 reduction electrode and the MH - 18 reduction electrode are 0.12Ω / cm 2 ; the resistance of the MH - 18_2μm reduction electrode is 0.11Ω / cm 2 .

[0215] The above embodiments are only examples, and the present invention is not limited thereto. Any technical idea that is substantially the same as the technical idea described in the claims of the present invention and has the same composition and the same function and effect belongs to the technical scope of the present invention.

Claims

1. A porous carbon body that satisfies the following physical properties: Physical property 1: The surface area of pores with a size of 2 nm or more and 5 nm or less obtained from the nitrogen desorption isotherm by the Barrett-Joyner-Halenda BJH method based on the Harkins-Jura formula is 100 m 2 / g to 500 m 2 / g, Physical property 2: The surface area of pores with a size of 2 nm or more and 100 nm or less obtained from the nitrogen desorption isotherm by the BJH method based on the Harkins-Jura formula is 200 m 2 / g to 1500 m 2 / g, Physical property 3: The nitrogen adsorption / desorption isotherm has a hysteresis loop, and in the relative pressure range of 0.3 to 1.0, the graph of the value obtained by subtracting the value of the nitrogen adsorption isotherm from the value of the nitrogen desorption isotherm according to the relative pressure, that is, the increment graph has at least a first maximum point and a second maximum point, and the value of the first maximum point located at a lower relative pressure is less than the value of the second maximum point located at a higher relative pressure.

2. The porous carbon body according to claim 1, wherein The maximum point ratio of the value of the first maximum point divided by the value of the second maximum point is 0.10 to 0.

95.

3. The porous carbon body according to claim 1, wherein The first maximum point is in the range where the relative pressure P / P0 is 0.4 or more and less than 0.9, and the second maximum point is in the range where the relative pressure P / P0 is 0.9 or more and less than 1.

0.

4. The porous carbon body according to claim 3, wherein The first maximum point is in the range where the relative pressure P / P0 is 0.45 or more and 0.80, and the second maximum point is in the range where the relative pressure P / P0 is 0.93 or more and 0.

98.

5. The porous carbon body according to claim 1, wherein In the nitrogen adsorption / desorption isotherm, the area ratio of the hysteresis loop area in the relative pressure region of P / P0 = 0.9 to 1.0 divided by the hysteresis loop area in the relative pressure region of P / P0 = 0.4 to 0.9 is 0.1 to 2.

0.

6. The porous carbon body according to claim 5, wherein The area ratio is 0.1 to 1.

5.

7. The porous carbon body according to any one of claims 1 to 6, wherein The porous carbon body further satisfies the following physical property 4: Physical property 4: Average interlayer spacing d measured by X-ray diffraction method 002 is from 0.335 nm to 0.350 nm.

8. The porous carbon body according to any one of claims 1 to 6, wherein The porous carbon body further satisfies the following physical property 5: Physical property 5: Lattice constant L in the a-axis direction measured by X-ray diffraction method a is 4 nm to 12 nm.

9. The porous carbon body according to any one of claims 1 to 6, wherein The relative pressure P / P0 of the closing point of the hysteresis loop is 0.45 or less.

10. The porous carbon body according to any one of claims 1 to 6, wherein In the increment graph, the value of the minimum point between the first maximum point and the second maximum point is 15% to 90% of the value of the first maximum point.

11. The porous carbon body according to any one of claims 1 to 6, wherein The porous carbon body is doped with a foreign element.

12. A catalyst for a fuel cell, comprising: A catalyst substance supported on the porous carbon body according to any one of claims 1 to 6.

13. A catalyst layer for a fuel cell, comprising: The catalyst according to claim 12 and an ionomer.

14. A polymer electrolyte membrane fuel cell, comprising: The catalyst according to claim 12.

Images