KR102357700B1 - S and n dual-doped graphitic porous carbon, a catalyst including the same and method for preparing the same - Google Patents

Abstract

The present invention comprises the steps of preparing a bulk graphite-type polymer by polymerizing a precursor containing sulfur and nitrogen elements; After mixing the bulk graphite-type polymer and the metal powder in an inert gas atmosphere, heat treatment at a temperature greater than or equal to the melting point of the metal; and washing the heat treatment product with an acid, a method for producing a sulfur and nitrogen double doped highly graphitic porous carbon body, a sulfur and nitrogen double doped highly graphitic porous carbon body prepared accordingly, and a fuel cell comprising the same and/or a water electrolysis reaction electrode catalyst.

Description

Sulfur and nitrogen double-doped highly graphitic porous carbon body, catalyst comprising same, and method for manufacturing the same

The present invention relates to a highly graphitic porous carbon body doped with sulfur and nitrogen, a catalyst comprising the same, and a method for preparing the same.

Technology using various natural resources such as solar, wind, and hydraulic energy as energy sources is being researched and developed. Fuel cell technology is an alternative clean energy because of its advantages such as: it does not emit air pollutants such as NOx; is being hailed as

A fuel cell is an energy conversion device that directly converts chemical energy possessed by fuel into electrical energy through an electrochemical reaction. A fuel cell system is constructed around a stack in which the fuel cell basic unit cells of the anode/electrolyte/cathode are connected in series and in parallel. It consists of a fuel processing device, a conversion device that converts DC power produced in the stack into AC power, and a heat recovery device that recovers heat.

이하로 다른 연료전지에 비해 매우 낮아 초기 시동성이 우수하고, 메탄올, 에탄올, 포름알데히드, 수소 등 다양한 화합물들을 연료로 사용함에 따라 청정 에너지원 측면에서 보다 바람직하다. 그러나, 이러한 장점들에도 불구하고, AFC, PEMFC 및 DMFC와 같은 저온형 연료전지는 산소환원반응 촉매로서 백금을 사용함에 따라, 상용화를 위해서는 고가의 촉매에 의한 고비용 문제를 해결해야 하며, 나아가, 백금 기반 촉매의 경우 입자의 이동, 응집, 침출, 성장 등의 요인들에 의해 열악한 내구성의 문제점 또한 존재한다. 이를 해결하기 위해, 미국, 일본, 유럽 등 세계적으로 크게 백금의 담지량을 줄이고 효과적으로 분산시키는 노력과 비백금 촉매 개발의 노력의 크게 두 가지의 노력이 이루어지고 있으나, 아직 비용 절감과 성능 향상 모두를 실용화 수준까지는 만족하지 못하고 있는 실정이다. 미국의 Dai 교수 연구팀에서는 H₂/O₂ 연료 전지용 무금속 산소 환원 촉매로 질소가 도핑된 수직 배양된 탄소 나노 튜브를 이용하여 백금(Pt) 촉매 보다 수명이 길고 성능이 약 4배 뛰어난 전극을 개발하였다 (2009, Science). 또한, 질소가 도핑된 그래핀을 이용하여 H₂/O₂ 연료 전지 촉매로서의 성능을 이미 평가하여 질소가 도핑된 탄소 나노 튜브와 비슷한 촉매 활성을 보인다는 보고도 이미 있었다 (2010, ACS Nano). 이 방법들은 질소가 도핑된 탄소 물질이 백금 촉매를 대체할 수 있다는 것을 보여준 아주 좋은 연구 결과라고 할 수 있다. 그러나, 이와 같은 질소가 도핑된 그래핀(질소 도핑 탄소체)일지라도 실제로 연료전지용 촉매로 사용해 보면 아직까지 산소 환원 활성도가 충분하지 못하고, 탄소체의 결정성(흑연성)이 낮아서 전기전도성과 안정성이 좋지 않다. 또한, 백금(Pt) 촉매를 그래핀(탄소체) 지지체에 담지하여 촉매를 구성하는 것이 일반적이나, 이 경우 Pt/탄소체 촉매의 내구성 등이 충분히 확보되지 않는다는 문제점이 있다. Fuel cells are alkaline fuel cell (AFC), phosphoric acid fuel cell (PAFC), polymer electrolyte fuel cell (PEMFC), molten carbonate fuel cell (MCFC), solid oxide fuel cell (SOFC), direct methanol fuel cell (DMFC) ), AFC, PEMFC and DMFC have an operating temperature of 100

Below, it is very low compared to other fuel cells, so it has excellent initial startability, and since various compounds such as methanol, ethanol, formaldehyde, and hydrogen are used as fuels, it is more preferable in terms of a clean energy source. However, despite these advantages, low-temperature fuel cells such as AFC, PEMFC, and DMFC use platinum as an oxygen reduction catalyst, so for commercialization, it is necessary to solve the problem of high cost due to an expensive catalyst, and further, platinum In the case of the base catalyst, there is also a problem of poor durability due to factors such as particle movement, agglomeration, leaching, and growth. In order to solve this problem, two major efforts are being made worldwide, such as the United States, Japan, and Europe, to greatly reduce and effectively disperse the amount of platinum supported, and to develop a non-platinum catalyst. The level is not satisfactory. Professor Dai's research team in the United States developed an electrode with a longer lifespan and about 4 times better performance than a platinum (Pt) catalyst using nitrogen-doped vertically cultured carbon nanotubes as a metal-free oxygen reduction catalyst for H ₂ /O ₂ fuel cells. (2009, Science). In addition, there have already been reports that nitrogen-doped graphene has been evaluated for performance as a H ₂ /O ₂ fuel cell catalyst and exhibits similar catalytic activity to nitrogen-doped carbon nanotubes (2010, ACS Nano). These methods are very good results of research showing that nitrogen-doped carbon materials can replace platinum catalysts. However, even with such nitrogen-doped graphene (nitrogen-doped carbon material), when it is actually used as a catalyst for fuel cells, oxygen reduction activity is not yet sufficient, and the crystallinity (graphite) of the carbon material is low, resulting in electrical conductivity and stability. Not good. In addition, it is common to configure the catalyst by supporting a platinum (Pt) catalyst on a graphene (carbon material) support, but in this case, there is a problem in that durability of the Pt/carbon material catalyst is not sufficiently secured.

Non-Patent Document 1 (Sulfur and Nitrogen Dual-Doped Mesoporous Graphene Electrocatalyst for Oxygen Reduction with Synergistically Enhanced Performance, Angewandte Chemie International Edition, 2012, 51, 11496-11500), graphene oxide and silica (SiO ₂ ) Nitrogen in a mixture After adding melamine as a precursor and benzyl disulfide (BDS) as a sulfur precursor, heat treatment at 900°C and Ar conditions, and then acid treatment with hydrogen fluoride (HF) to remove silica to synthesize nitrogen and sulfur doped carbon bodies However, although heat treatment for carbonization was performed at a relatively high temperature (900 ℃), it showed low carbon crystallinity (ID /I _G = ~0.92 ₎ in the Raman spectrum. It is difficult to apply because the process is rather complicated in that it requires a two-step process.

Patent Document 1 (KR 10-2016-0105152A) prepares a mixed solution by mixing an S or N-containing precursor and an alkali metal source, carbonization, and acid treatment (hydrochloric acid) to synthesize an S or N-doped carbon body, The alkali metal used is a group 1 metal such as lithium, sodium, and potassium, and has a very strong reducing power and reacts explosively with atmospheric air and water, so it is very dangerous to actually apply the inventions. Practical application is difficult in that it is necessary to pay attention to deoxygenation and dehydration in the reaction solution used with the present invention. In addition, NaOH used in the embodiment is a process frequently used as a method of activating a carbon body in the carbonization process (through layer separation by metal intercalation, micropores develop and specific surface area increases). It is also undesirable in that the micropores of the carbon body produced by the reaction are developed, so the crystallinity is low, and an additional heat treatment is required because a functional group containing oxygen is included.

Patent Document 2 (JP 2012-153555A) mixes a precursor compound having one or more heteroatoms such as nitrogen and sulfur with an alkali metal, heat-treats at 100 to 400 ° C, and then thermally decomposes at 250 to 1,500 ° C to contain hetero atoms Although a pin is synthesized, it is difficult to apply for the same reason as in Patent Document 1 described above.

Patent Document 3 (KR 10-2016-0129938A) forms a complex in powder state by mixing a precursor containing sulfur and a silica template, and forms crystalline carbon by using a silica template and heating at 800 to 900 ° C. , a carbon catalyst having a porous structure is prepared by washing it with acid to remove the used silica template, and the precursor thiourea and thioacetamide containing sulfur are disclosed as specific examples, but silica added to form mesopores The template does not contribute to increasing the crystallinity of the carbon body during carbonization, and it is not good in terms of process efficiency because it has to be treated in a strong acid or strong base condition to dissolve and remove it.

There is a need for a carbon body manufacturing technology that dramatically increases the crystallinity of carbon in a low-temperature reaction (below 1,000 °C) and simultaneously forms mesopores while doping with a defective heteroelement.

One embodiment comprises the steps of preparing a bulk graphite-type polymer by polymerizing a precursor containing sulfur and nitrogen elements; After mixing the bulk graphite-type polymer and the metal powder in an inert gas atmosphere, heat treatment at a temperature greater than or equal to the melting point of the metal; and washing the heat treatment product with acid.

The sulfur and nitrogen element-containing precursor may be at least one selected from the group consisting of thiourea, ammonium thiocyanate, and thioacetamide.

The sulfur- and nitrogen-containing precursor includes a sulfur-containing precursor and a nitrogen-containing precursor, and the sulfur-containing precursor includes benzyl disulfide, thiophene, and 2,2'-dithiophene (2,2'). -dithiophene), p-toluenesulfonic acid and 2-thiophenemethanol may be an organic molecule precursor or a polymer precursor comprising at least one selected from the group consisting of, the nitrogen-containing Precursors are amino acids such as guanine, adenine, and purine, melamine, urea, pyridine, aniline, dicyandiamide, ethylenedia It may be an organic molecule or a polymer precursor including at least one selected from the group consisting of ethylenediamine and ethylenediaminetetraacetic acid (EDTA).

The metal powder may be an alkaline earth metal powder.

The bulk graphite-type polymer and the metal powder may be mixed in an N+S:M atomic molar ratio of 1:0.3 to 1:5. In this case, N and S are nitrogen and sulfur included as hetero elements in the bulk graphite polymer, respectively, M is a metal element of the metal powder, and N+S is the sum of the nitrogen and sulfur atoms.

Another embodiment provides a highly graphitic porous carbon material doped with sulfur and nitrogen, wherein the intensity ratio of the peak measured by the Raman spectrum satisfies the following Relations 1 and 2.

[Relational Expression 1]

0 ≤ I _D /I _G ≤ 0.95

[Relational Expression 2]

0.3 ≤ I _2D /I _G ≤ 2

In Relations 1 and 2, I _D is the peak intensity of the D band (near 1,350 cm ⁻¹ ) in the Raman spectrum, I _G is the peak intensity of the G band (near 1,580 cm ⁻¹ ) in the Raman spectrum, and I _2D is the Raman spectrum is the peak intensity of the 2D band (near 2,700 cm ^-1 ).

The carbon body may satisfy the following Relational Equation 3.

[Relational Expression 3]

V ₁ /V ₂ ≤ 0.5

In Relation 3, V ₁ is the volume of micropores of the carbon body (cm ³ /g), and V ₂ is the volume of the mesopores of the carbon body (cm ³ /g).

The carbon body may include mesopores having a volume of 0.3 to 1.8 cm ³ /g.

The carbon body may include 0.3 to 5.0 atomic % of N as a hetero element, and 0.1 to 1.5 atomic % of S.

The carbon body may have a BET specific surface area of 80 to 1,000 m ² /g.

Another embodiment provides a fuel cell and/or water electrolysis electrode catalyst comprising the sulfur and nitrogen doped highly graphitic porous carbon body.

The fuel cell and/or water electrolysis reaction electrode catalyst is platinum (Pt), rhodium (Rh), ruthenium (Ru), nickel (Ni), cobalt on the surface and inside of the porous sulfur and nitrogen double doped highly graphitic carbon body (Co), iron (Fe), palladium (Pd), copper (Cu), iridium (Ir), osmium (Os), molybdenum (Mo), vanadium (V), or a combination thereof may be supported. .

The present invention combines with nitrogen with a strong reducing power to separate the sp2 carbon of the precursor from nitrogen by introducing an alkaline earth metal into the carbonization process, allowing for easier carbon-to-carbon bonding, even for samples treated at a low temperature of 650 ~ 1000 ℃ It can have large carbon crystallinity in the Raman spectrum.

That is, the present invention can secure high crystallinity at a low temperature, thereby preventing the loss of hetero element (sulfur and nitrogen) doping amount at high temperature, and also secure high crystallinity of the carbon body and use it through acid treatment at the same time It is possible to provide a method for producing a porous carbon body and a carbon body having a specific surface area of 80 to 1000 m ² /g by removing the removed alkaline earth metal to secure porosity including mesopores at the removed site.

1 (a) is a schematic diagram showing the synthesis process of a sulfur and nitrogen double-doped highly graphitic porous carbon body and a catalyst comprising the same according to an embodiment of the present invention;
2 is a: a graph showing the results of X-ray diffraction spectroscopy (XRD) analysis for SCNMg-X (950, 850 and 750 ° C.), SCN, and graphite, b: a graph showing the Raman spectrum analysis, c: nitrogen adsorption and desorption A graph showing the isotherm, d: a graph showing the electrical conductivity according to the relative pressure change,
3 is an X-ray diffraction spectroscopy (XRD) analysis graph for SCNMg-850-ASP before removal of Mg by acid washing;
4 is a photograph showing a comparison of the products (SCNMg-850-ASP, SCN-850) remaining after heat treatment in an alumina crucible;
5 shows SEM and TEM images of (a,e) SCN, (b,f) SCNMg-750, (c,g) SCNMg-850, (d, h) SCNMg-950,
6 is a graph showing the chemical composition analysis results of SCNMg-850 and SCN using Vairo MACRO cube elemental analyzer;
7a to 7c show XPS spectra for SCNMg-850 and SCN, (7a) C 1s spectrum, (7b) N 1s spectrum, (7c) S 2p spectrum, and FIG. 7 d and e are SCN and SCN, respectively. Schematic diagram of SCNMg-X,
Figure 8 is (a) SCN and (b) O 1s XPS spectrum of SCNMg-850,
9 is a: XRD analysis result of SCNMg-850-YRh-500 (Y is 73, 36, 18), b: TEM image of SCNMg-850-36Rh-500, c: SCNMg-850-36Rh-500 HAADF-STEM (High-angle annular dark-field scanning TEM) image for , d: HR-TEM image for SCNMg-850-36Rh-500, e: Ultra HR-TEM image for SCNMg-850-36Rh-500, f: Image showing the crystal lattice lines by magnifying the boxed portion of 9d;
Figure 10 is EDS (Energy dispersion spectroscopy) mapping for SCNMg-850-36Rh-500,
11 is a TEM image for (a, b) SCNMg-850-18Rh-500 and (c, d) a TEM image for SCNMg-850-73Rh-500;
12 shows (a) LSV polarization curves for SCNMg-850-18Rh-500, SCNMg-850-36Rh-500, SCNMg-850-73Rh-500 and commercial Pt/C (Pt content: 20% and 46%). (b) EIS Nyquist plots;
(c) LSV polarization curves, for SCNMg-850-36Rh-500, SCNMg-850-36Rh-700, SCNMg-850-36Rh-900 and commercial Pt/C (Pt content: 20% and 46%),
(d) LSV polarization curves for SCNMg-850-36Rh-500, rGO-36Rh-500, VC-36Rh-500, SCN-36Rh-500, and commercial Pt/C (Pt content: 20% and 46%) (e) EIS Nyquist plots;
(f) TOF curves for SCNMg-850-36Rh-500 and commercial Pt/C (Pt content: 46%).
13 is a TGA (Thermogravimetric analysis) analysis graph of SCNMg-850-36Rh-500, VC-36Rh-500, and rGO-36Rh-500;
14 is an XRD analysis graph of SCNMg-850-36Rh-500, SCNMg-850-36Rh-700, and SCNMg-850-36Rh-900;
15 is (a) SCNMg-850-36Rh-500; (b) SCNMg-850-36Rh-700; and (c) TEM images of SCNMg-850-36Rh-900,
16 shows (a, b) VC-36Rh-500; (c, d) rGO-36Rh-500; and (e, f) TEM images of SCN-36Rh-500,
17 is (a) N ₂ adsorption/desorption isothermal graph and pore size distribution graph of SCN, SCNMg-850, VC, and rGO; (b) Raman spectral analysis; and (c) a graph measuring electrical conductivity;
18 is (a) SCNMg-850-36Rh-500; (b) 46% Pt/C; (C) CV curves measured at different scan rates in 0.1~0.3V potential window of each GC electrode, and (d) SCNMg-850-36Rh-500, 46% Pt/C, and double layer capacitance for GC electrodes. This is the graph shown.

Advantages and features of the present invention and methods of achieving them will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in a variety of different forms, and only these embodiments allow the disclosure of the present invention to be complete, and common knowledge in the technical field to which the present invention belongs It is provided to fully inform the possessor of the scope of the invention, and the present invention is only defined by the scope of the claims. With reference to the accompanying drawings will be described in detail for the implementation of the present invention. Irrespective of the drawings, like reference numbers refer to like elements, and "and/or" includes each and every combination of one or more of the recited items.

Unless otherwise defined, all terms (including technical and scientific terms) used in this specification may be used with meanings commonly understood by those of ordinary skill in the art to which the present invention belongs. In the entire specification, when a part "includes" a certain component, this means that other components may be further included, rather than excluding other components, unless otherwise stated. The singular also includes the plural, unless the phrase specifically states otherwise.

In this specification, when a part of a layer, film, region, plate, etc. is “on” or “on” another part, this includes not only the case where it is “directly on” the other part, but also the case where there is another part in between. do.

One embodiment of the present invention provides a method for preparing a highly graphitic porous carbon body doped with sulfur and nitrogen. The manufacturing method comprises the steps of preparing a bulk graphite-type polymer by polymerizing a precursor containing sulfur and nitrogen elements; After mixing the bulk graphite-type polymer and the metal powder in an inert gas atmosphere, heat treatment at a temperature greater than or equal to the melting point of the metal; and washing the heat treatment product with an acid.

In the bulk graphite-type polymerization step, since the hybrid orbital of carbon is transformed from sp3 to sp2, there is an advantage in that the crystal structure arrangement to be changed to crystalline carbon (sp2) in the subsequent heat treatment step (carbonization step) is easy. On the other hand, in the case of carbonization using a monomolecular precursor without the polymerization step, since the hybridization of carbon and the crystal structure arrangement must be simultaneously made during the carbonization process, the content of hetero elements is greatly reduced, and the process efficiency is not good.

In the step of polymerizing the precursor, the precursor containing sulfur and nitrogen elements is put into an airtight container, and the temperature increase rate is 1.0 ~ 5.0 ℃ / min, the reaction temperature is 300 ~ 1,000 ℃ 1 ~ 6 hours, preferably the temperature increase rate 2.0 ~ 4.5 ℃/min, the reaction temperature may be 300 ~ 700 ℃ for 3 to 6 hours to react.

The sulfur and nitrogen element-containing precursor may be at least one selected from the group consisting of thiourea, ammonium thiocyanate, and thioacetamide. The above-mentioned precursor is an organic compound that has a high nitrogen-to-carbon content and is easily decomposed at a low temperature and is difficult to be polymerized. On the other hand, oxygen element, which may be included as a hetero element in the produced carbon body, is not preferable because it corresponds to a defect and reduces crystallinity of the carbon body and requires additional heat treatment to remove it.

On the other hand, in addition to the precursor containing sulfur and nitrogen elements at the same time as described above, it is also possible to use a precursor separately mixed with the sulfur-containing precursor and the nitrogen-containing precursor. As the sulfur-containing precursor, benzyl disulfide, thiophene, 2,2'-dithiophene, p-toluenesulfonic acid, and 2- It may be an organic molecule or polymer precursor containing at least one selected from the group consisting of thiophenemethanol, and the nitrogen-containing precursor includes amino acids such as guanine, adenine, and purine. The group consisting of urea, melamine, urea, pyridine, aniline, dicyandiamide, ethylenediamine and ethylenediaminetetraacetic acid (EDTA) It may be an organic molecule or a polymer precursor comprising at least one selected from

As a non-limiting example, a precursor obtained by mixing the sulfur-containing precursor and the nitrogen-containing precursor in a weight ratio of 5:5 to 1:9 may be used, specifically, a weight ratio of 5:5 to 4:6, 3:7 to 2 A precursor mixed in a weight ratio of :8 or 1.5:8.5 to 1:9 may be used. Alternatively, a mixed precursor may be used such that the ratio of the number of moles of the S element of the sulfur-containing precursor to the number of moles of the N element of the nitrogen-containing precursor is 1:1 to 1:2.5, specifically 1:1 to 1:1.2, 1:1.5 to 1:1.7, or 1:2 to 1:2.5, a mixed precursor may be used. In this case, there is an advantage in that nitrogen and sulfur doping amounts can be individually and precisely controlled in consideration of the degree of disappearance of each doping element in the carbonization process.

The bulk graphite-type polymer may include 30 to 90 wt% of sulfur-doped graphitic C ₃ N ₄ (S-doped graphitic C ₃ N ₄ ), preferably 50 to 70 wt%, based on the total weight. Since its atomic arrangement and hybrid orbital are similar to the graphene structure, it is very advantageous for the carbon hexagonal structure formation in the carbonization step and the crystallinity of the carbon body can be increased.

In addition, the prepared bulk graphite-type polymer may contain 40 to 80 atomic% or 40 to 60 atomic% of N as a hetero element, and 0.01 to 10 atomic% or 0.01 to 5 atomic% of S. Sulfur and nitrogen doping can enhance the adsorption of reactive species in hydrogen evolution reactions with carbon bodies. Specifically, nitrogen and sulfur contained in the carbon structure have high electron affinity compared to carbon and have a lone pair of electrons, so it is easy to form an electronic structure favorable for the reaction, and thus, it is suitable for hydrogen generation reaction/oxygen reduction reaction. It is easy to provide a suitable site (site). However, if the N content exceeds 80 atomic % or the S content exceeds 10 atomic %, it is easily decomposed during manufacture of the carbon body, making it difficult to form a bond between carbons, and its crystallinity is poor. If it is less than, the activity of the hydrogen evolution reaction/oxygen reduction reaction is not sufficient, which is disadvantageous.

Then, after mixing the prepared bulk graphite polymer and the metal powder in an inert atmosphere, heat treatment is performed at a temperature equal to or higher than the melting point of the metal.

In the heat treatment step (carbonization step), as the molten metal powder is entirely applied to the surface of the bulk graphite-type polymer, metal-nitride or metal-sulfide can be well formed by the high reducibility of the metal. If there is no metal-nitride or metal sulfide formation, doping nitrogen and sulfur are decomposed at a temperature of about 600 ° C. or higher during heat treatment, so increasing the heat treatment temperature is disadvantageous in terms of loss of doping nitrogen and sulfur. Conversely, as the heat treatment temperature is lowered, the synthesized carbon Although the graphiticity of the sieve is poor, the above problem can be prevented in the present invention.

The heat treatment temperature may be 1,000 °C or less, preferably 650 to 1,000 °C, more preferably 650 to 950 °C, or 700 to 900 °C, most preferably 800 to 900 °C. In addition, the metal powder can effectively suppress the loss of doping nitrogen and sulfur when the melting point of the metal is 1,000 ℃ or less. Specifically, if the melting point of the metal is less than 1,000 ° C, 950 ° C or less, 900 ° C or less, 800 ° C or less, or 750 ° C or less, the metal powder is partially melted at a temperature (600 ° C) at which the loss of doping nitrogen or sulfur occurs to obtain bulk graphite. It is possible to prevent the problem of not completely covering the surface of the type polymer. In addition, as a preferred lower limit value of the melting point of the metal, when all of the metal powder is melted at too low a temperature, when it is more than 50 ° C, 100 ° C or more, 150 ° C. Problems that are difficult to handle can be avoided.

The metal powder may be an alkaline earth metal powder, for example, magnesium (Mg) or calcium (Ca), preferably magnesium. Representative reducing metals applied in the reduction process of metals are calcium, aluminum, and magnesium in order of reducing power, but calcium has a high melting point of 850 ° C. Disadvantageous, aluminum has excellent stability, easy handling, and good reducing power, but has a disadvantage in that it is difficult to remove AlN, Al ₂ O ₃ , etc. mixed after the reduction process. On the other hand, magnesium has a relatively low melting point of 650° C., is easy to handle, and has excellent reducing power, so it is most preferable for application to the present invention. In addition, the metal particle diameter of the metal powder may be 70 ~ 100㎛ or 40 ~ 70㎛. When the particle diameter exceeds 100 μm, it is difficult to uniformly mix with the bulk graphite-type polymer and is disadvantageous in forming uniform mesopores. When the particle diameter of the metal particles is less than 40 μm, it is difficult to maintain the metallic surface by reacting with atmospheric oxygen or water, which is disadvantageous in reactivity and reducing power.

Meanwhile, the particle diameter of the metal particles may mean D50, and D50 means the particle diameter when the cumulative volume becomes 50% from a small particle diameter in particle size distribution measurement by a laser scattering method. Here, D50 can measure the particle size distribution using Malvern's Mastersizer3000 by taking a sample according to KS A ISO 13320-1 standard for metal particle material. Specifically, after dispersing using ethanol as a solvent and using an ultrasonic disperser if necessary, the volume density may be measured, but the present invention is not limited thereto.

In the heat treatment step, the bulk graphite polymer and the metal powder may be mixed in a weight ratio of 1:0.5 to 1:2, preferably 1:0.7 to 1:1.5 by weight, more preferably 1:0.9 to 1:1.1 It may be mixed in a weight ratio, most preferably about 1:1 weight ratio. In addition, the bulk graphite polymer and the metal powder may be mixed in an N+S:M atomic molar ratio of 1:0.3 to 1:5, preferably 1:0.5 to 1:2, more preferably 1:0.7 to 1 : 1.5 molar ratio, more preferably 1:0.9 to 1:1.1 molar ratio, most preferably about 1:1 molar ratio may be mixed. When the bulk graphite-type polymer and the metal powder are included in the above content, the formation of metal-nitride and metal-sulfide can be optimized as described below. Meanwhile, N and S are nitrogen and sulfur contained as hetero elements in the bulk graphite polymer, respectively, M is a metal element of the metal powder, and N+S is the sum of the nitrogen and sulfur atoms.

The heat treatment may be performed in an inert gas flow atmosphere, for example, a nitrogen flow atmosphere or an argon flow atmosphere, but is not limited thereto.

Then, the heat treatment product is washed with an acid to remove the excess metal powder and metal-nitride and metal-sulfide as by-products by etching. As such an etching effect, a mesopore structure (formation of mesopores with a size of 2 to 50 nm) can be formed at the site where the residual metal powder, metal-nitride, and metal-sulfide are removed from the carbon body. The residual metal powder, metal nitride, and metal sulfide may be, for example, residual magnesium powder (Mg), magnesium nitride (Mg ₂ N ₃ ) and magnesium sulfide (MgS) having a uniform size of 20 to 50 nm, and the By being removed by acid washing, a carbon body having mesopores can be prepared. In particular, since the mesopore structure tends to have a larger pore structure as the carbonization heat treatment temperature increases, a low-temperature carbonization process is essential. In addition, it is analyzed that the effect of magnesium nitride on the formation of mesopores is greater than that of residual magnesium, and magnesium with a particle size level of several tens of μm (70 ~ 100 μm, or 40 ~ 70 μm) is used in the reaction to be uniformly distributed in the liquid phase. It may be possible by forming magnesium nitride of a size (20-50 nm).

In particular, as the mesopore structure is formed by acid etching after heat treatment at a relatively low temperature, the pore structure uniformly formed inside and on the surface of the carbon body can contribute to the improvement of the specific surface area. On the other hand, in the case of increasing the crystallinity of a carbon body by a simple high-temperature heat treatment in the prior art, not only nitrogen and sulfur are lost, but also the micropores are closed, and there is a problem in that the specific surface area is rather decreased.

In the acid washing, specifically, the heat treatment product is added to a 0.5 to 3.5 M acid solution, for example, a 1 to 3 M inorganic acid (hydrochloric acid (HCl), phosphoric acid (H ₂ PO ₄ ) or sulfuric acid (H ₂ SO ₄ )) solution, and It may be to perform acid washing by stirring for 1 to 10 hours, preferably 2 to 8 hours, and then filtering the recovered product with deionized water or the like and drying to obtain a carbon body, but the present invention does not provide for this It is not limited.

Another embodiment of the present invention provides a highly graphitic carbon body doped with porous sulfur and nitrogen. In the carbon body, the intensity ratio of the peak measured by the Raman spectrum may satisfy the following Relations 1 and 2.

[Relational Expression 1]

0 ≤ I _D /I _G ≤ 0.95

[Relational Expression 2]

0.3 ≤ I _2D /I _G ≤ 2

In Relations 1 and 2, I _D is the peak intensity of the D band (near 1,350 cm ⁻¹ ) in the Raman spectrum, I _G is the peak intensity of the G band (near 1,580 cm ⁻¹ ) in the Raman spectrum, and I _2D is the Raman spectrum is the peak intensity of the 2D band (near 2,700 cm ^-1 ).

In the above relation 1, I _D /I _G is preferably 0.8 or less, more preferably 0.7 or less or 0.6 or less. The _ID is a peak indicating defects in the crystal of the carbon body, and in the case of graphene, it is known to be observed near the edge of the specimen or when there are many defects in the specimen. I _G is a peak commonly found in graphitic materials and is a measure of graphitization crystallinity. The carbon body of the present invention can secure high crystallinity of the carbon body in the relatively low-temperature carbonization step and suppress the loss of nitrogen and sulfur as the above relational formula 1 is satisfied. Meanwhile, the lower limit of I _D /I _G may be, for example, 0.1 or more or 0.2 or more.

In Relation 2, I _2D /I _G may be preferably 0.8 to 1.7, and more preferably 0.9 to 1.6. The I _2D tends to be inversely proportional to the number of graphene layers, and in the case of an ideal single-layer graphene close to the actual definition, I _2D /I _G shows a peak intensity close to 2. As the present invention falls within the I _2D /I _G range, the carbon body of the present invention may be graphene consisting of less than 5 layers, preferably 1 to 3 layers, and more preferably 1 to 2 layers.

In addition, the carbon body may satisfy the following relation (3).

[Relational Expression 3]

V ₁ /V ₂ ≤ 0.5

In Relation 3, V ₁ is the volume of micropores of the carbon body (cm ³ /g), and V ₂ is the volume of the mesopores of the carbon body (cm ³ /g).

Specifically, V ₁ /V ₂ ≤ 0.3 or V ₁ /V ₂ ≤ 0.1, preferably V ₁ /V ₂ ≤ 0.08 or V ₁ /V ₂ ≤ 0.05, more preferably V ₁ /V ₂ ≤ 0.02, V ₁ /V ₂ ≤ 0.01.

In general, a micropore means a pore having a size of 2 nm or less, and a mesopore means a pore having a size of 2 to 50 nm. The pores formed on the surface and inside of the carbon body are a type of defect and mean low crystallinity. In addition, the increase in specific surface area is increased by the formation of pores, and in particular, the effect of micropores with small pore sizes is greater than that of mesopores. In the case of the present invention, carbonization using metal powder can form fewer micropores by increasing the crystallinity of the carbon body, and as many mesopores are formed through the acid washing process, the specific surface area is somewhat lower than that of the prior art, but By increasing the mesopores, it is more advantageous in terms of mass transfer in the application reaction, and the crystallinity of the carbon body can be secured. Specifically, it is advantageous for the movement and delivery of reactants, intermediates, and products in oxygen reduction reaction and hydrogen evolution reaction due to the above-described mesopores, and in particular, when supporting Pt and Rh catalyst materials, reactants (water in water electrolysis reaction, It facilitates the access of OH ^- ions), and the release of the product (hydrogen gas) is easy. The mass transfer of these application reactions has a greater effect in mesopores than in micropores.

On the other hand, the carbon body may have a total pore volume of 0.3 to 2.0 cm ³ /g, a micropore volume of 0.001 to 0.025 cm ³ /g, a mesopore volume of 0.3 to 1.8 cm ³ /g, and an average pore size of 10 to 50 nm, Preferably, the total pore volume is 0.5 to 1.3 cm ³ /g, the micropore volume is 0.005 to 0.020 cm ³ /g, the mesopore volume is 0.5 to 1.3 cm ³ /g, and the average pore size is 15 to 40 nm. In addition, the BET specific surface area of the carbon body may be 80 to 1000 m ² /g, preferably 100 to 500 m ² /g, more preferably 150 to 400 m ² /g.

On the other hand, the BET specific surface area was calculated using the BET (Brunauer-Emmett-Teller) method based on the nitrogen adsorption result at a relative pressure in the range of 0.05 to 0.2, and the total pore volume was calculated through the gas adsorption amount at 0.99 relative pressure. did In addition, the mesopore size was measured by the BJH method (Barrett-Joyner-Halenda) based on the Kelvin equation, and the mesopore volume was analyzed using the amount of nitrogen adsorbed at a relative pressure of 0.95 or less.

The carbon body may include 0.3 to 5.0 atomic % of N as a hetero element, and 0.1 to 1.5 atomic % of S. Preferably it may contain 0.6 to 3.8 atomic % N and 0.1 to 1.0 atomic % S. Since doping of nitrogen and sulfur is also a type of defect in the carbon body, if the amount of doping is large, crystallinity is reduced and electrical conductivity is deteriorated. For electrochemical application, a balance between the degree of doping of the hetero element and the crystallinity of the carbon body is required, and it may be preferable when hetero elements N and S are included in the above-mentioned range. In addition, the present invention can be improved more quantitatively by controlling the type and content of the metal powder.

On the other hand, the carbon body may include a bonding state of pyrrolic N (Pyrrolic N), graphitic N (Graphitic N), pyridinic N (Pyridinic N) or a combination thereof, and also hetero element nitrogen (N) With respect to 100 atomic %, 10 atomic % or more, preferably 30 atomic % or more, more preferably 50 atomic % or more may be present in a bonded state of pyrrolic N, and as a non-limiting example, the upper limit is 60 atomic % or less, 50 atomic % or less, or 40 atomic % or less, Graphitic N may be 50 atomic % or less, Pyridinic N may be 20 atomic % or more, preferably 50 atomic % or less % or more, more preferably 60 atomic% or more. In particular, since the unshared electron pair of pyrrolic N is not involved in aromatic stabilization, it is known that the binding energy is lower than that of graphitic N, pyridinic N, and the like. In the present invention, since the ratio of pyridinic N among doped N is relatively high, the crystallinity of the nitrogen-doped carbon body can be improved and the activity of oxygen reduction reaction and hydrogen evolution reaction can be improved. However, the relative proportion of N species present may vary depending on the carbonization temperature, time, and metal powder used.

Another embodiment provides an electrode catalyst for a fuel cell and/or a water electrolysis reaction including the carbon body. The carbon body includes platinum (Pt), rhodium (Rh), nickel (Ni), cobalt (Co), iron (Fe), palladium (Pd), copper (Cu), iridium (Ir), osmium ( Os), molybdenum (Mo), vanadium (V), etc. or a combination thereof may be supported.

The water electrolysis reaction is a technology for producing hydrogen and oxygen from pure water using electrical energy, and is largely divided into alkaline water electrolysis, solid polymer electrolyte (PEM) water electrolysis, and high-temperature steam electrolysis technology using solid oxide. The highly graphitic porous carbon material doped with sulfur and nitrogen of can be used not only as an electrode catalyst for fuel cells but also as an electrode catalyst for water electrolysis.

Hereinafter, preferred examples and comparative examples of the present invention will be described. However, the following examples are only preferred examples of the present invention, and the present invention is not limited thereto.

Example

Examples 1-3

1) Manufacture of bulk graphite-type polymer (hereinafter referred to as SCN)

After putting 10 g of thiourea (Sigma Aldrich, 99%) in an alumina boat and sealing it (cover), the bulk was heat treated in a tube furnace at 500 °C at a temperature increase rate of 5 °C/min under nitrogen atmosphere for 2 hours. A graphite-type polymer (hereinafter referred to as SCN) was obtained as a yellow powder.

2) Preparation of porous sulfur and nitrogen double doping highly graphitic carbon body (hereinafter referred to as SCNMg-X)

3 g of the obtained SCN was mixed with Mg powder (Sigma Aldrich, 99%) of the same weight for 20 min using a ball mill, and the well-mixed mixed powder was put into an alumina crucible and an argon (Ar) flow atmosphere ( flow rate of 200mL/min), heat treatment for 5 hours in a tube furnace at a temperature of X°C (750°C, 850°C, 950°C, Examples 1 to 3) according to each example at a temperature increase rate of 50°C/min to black powder (hereinafter referred to as SCNMg-X-ASP) was obtained.

Then, the heat-treated product was added to a 0.5MH ₂ SO ₄ solution and stirred at 80° C. for 12 hours to perform acid leaching. The recovered product was filtered with deionized water and vacuum dried at 70° C. to obtain a highly graphitic porous carbon body doped with sulfur and nitrogen (hereinafter referred to as SCNMg-X).

evaluation example

[Assessment Methods]

* Material property evaluation method

To analyze the prepared porous carbon body, X-ray diffraction analysis was performed using a Rigaku Smartlab X-ray diffraction apparatus, and Cu-Kα (λ=0.15418 nm) rays were used for 30kV, 40mA, scan rate 4°/min. was performed with

For the FT-IR (Fourier transform infrared) spectrum, NICOLET CONTINUUM was used.

Transmission electron microscopy (TEM EM912 Omega) observations were performed at 120 kV, and high-resolution TEM (HR-TEM) and STEM images were obtained using a JEOL FE-2010 microscope operated at 200 kV. Scanning electron microscopy (SEM) observations were performed using a Hitachi S-4700 microscope operating at an accelerating voltage of 10 kV.

Nitrogen adsorption-desorption isotherms were measured at -196 °C using a Micromeritics ASAP 2460 Accelerated Surface Area and Porosity Analyzer after degassing the samples at 150 °C to 20 mTorr for 12 h.

The BET specific surface area was calculated using the Brunauer-Emmett-Teller (BET) method based on the nitrogen adsorption results at a relative pressure in the range of 0.05-0.2.

Raman analysis was performed using a Raman spectrometer (Renishaw spectrometer). A 514.5 nm laser beam (Ar+ ion) was used.

X-ray photoelectron spectroscopy (XPS) analysis was performed using an ESCALAB 250 XPS system using monochromated Al Kα (150 W).

The metal loading in the thermal response of all samples was determined by thermogravimetric analysis (TGA) using a Bruker TG-DTA3000SA analyzer. Heating rate of 5 ℃/min, inflowing air, the temperature was raised from room temperature to 1000 ℃.

[Evaluation Example 1] Characteristic analysis results such as high crystallinity of carbon body

Figure 2 is a carbon support X-ray diffraction spectroscopy (XRD) analysis results (a), Raman spectrum analysis (b), and N ₂ adsorption and desorption isotherms (c) and electricity according to pressurization pressure according to Examples and Reference Examples It is a graph showing the conductivity (d).

In Figure 2 (a), SCN vs. SCNMg-X (750, 850 and 950 ° C) shifted to a 25.85 ° peak indicating graphite versus SCN showing a peak at 27.5 ° position corresponding to the (002) plane by lamination of graphite polymer Thus, high crystallinity can be confirmed in the final product.

Meanwhile, referring to FIG. 3 , in the case of SCNMg-850-ASP obtained before acid leaching after magnesium thermal reduction, it can be seen that Mg ₃ N ₂ , MgS, and MgO are formed, which is a small amount of nitrogen during the magnesium thermal reduction process. and sulfur is formed from Mg ₃ N ₂ and MgS in the SCN frame.

In Figure 2 (b), SCNMg-X compared to SCN, it can be seen that new peaks are generated in the D band (1350 cm ^-1 ), the G band (1600 cm ^-1 ) and the 2D band (2700 cm ^-1 ). The results of Raman spectrum analysis of Examples 1 to 3 are summarized in Table 1 below. Referring to Table 1 below, it can be seen that SCNMg-X has high crystallinity, and is composed of less than about 5 graphene layers, preferably about 2 to 3 graphene layers, and more preferably about 1 to 2 graphene layers. have.

Sample

The number of graphene layers SCNMg-750 0.92 0.5 <5 SCNMg-850 0.69 0.9 2-3 SCNMg-950 0.66 1.5 1-2 SCN - - -

On the other hand, without Mg, almost all of SCN-850 was decomposed during high-temperature treatment, so sample recovery was difficult (see FIG. 4), Raman spectrum analysis could not be performed, and it was difficult to use as a carbon catalyst for fuel cells or hydrogen generation reaction. Confirmed.

In FIG. 2(c), nitrogen adsorption and desorption isotherms were measured, and the calculated specific surface area (BET), micropore volume, mesopore volume, total pore volume and average pore size of SCN, SCNMg-X are shown in Table 2 below. arranged in Referring to FIG. 2 (c), it can be confirmed that micropores exist at isothermal low pressure (P/P ₀ < 0.01), and SCNMg-X abruptly increases the amount of nitrogen adsorption in the range of 0.5 to 0.8 P/P ₀ appears, which proves the presence of mesopores, and the increase in nitrogen adsorption in the range of 0.9 to P/P ₀ explains the presence of macropores.

Sample BET surface area (m ² /g) Total pore volume(cm ³ /g) Micropore volume (cm ³ /g) Mesopore volume (cm ³ /g) Average pore size diameter (nm) SCN 9.46 0.033 0.004 0.029 13.753 SCNMg-750 223.92 0.961 0.007 0.954 16.729 SCNMg-850 253.64 1.069 0.004 1.065 16.291 SCNMg-950 157.51 0.825 0.016 0.809 20.258

From Table 2 and FIG. 2(c), it can be seen that the specific surface area of the Example of the present invention is greatly improved compared to that of SCN. Specifically, it can be seen that SCNMg-X has increased specific surface area, total pore volume, and mesopore volume compared to SCN, and the average pore size is also increased. This phenomenon occurs because magnesium vapor penetrates into the SCN during carbonization and reacts with nitrogen and sulfur to form magnesium nitride and sulfide, and the tri-s-triazine ring structure of SCN is disrupted, and then magnesium nitride and sulfide are removed during acid leaching. It is analyzed that this is because pores are formed in the carbon structure by In particular, it can be seen that the volume increase of the mesopores compared to the micropores is remarkable. As described above, the mesopores have a low contribution to the increase of the specific surface area, so they are good for improving the crystallinity of the carbon body and are advantageous in terms of delivery of applied materials.

In FIG. 2(d), it can be seen that SCNMg-X has improved electrical conductivity compared to SCN, and thus, it can be predicted that the electrocatalytic activity is improved because the charge transfer resistance is very low. This phenomenon is analyzed because SCNMg-X forms high graphitic (high crystallinity), bilayer to 10 multilayer graphene.

[Evaluation Example 2] Morphology analysis of carbon bodies

From FIG. 5, SCN shows a big junk-type structure with low porosity (SEM and TEM images of SCN: refer to FIGS. It can be confirmed that it has a honeycomb-like structure having a degree. That is, the SEM images of SCNMg-X can be seen in FIGS. 5 (b) to 5 (d), and the TEM images can be seen in FIGS.

[Evaluation Example 3] Analysis of the chemical composition of carbon bodies, etc.

6 is a graph showing the chemical composition analysis results of carbon bodies using Vairo MACRO cube elemental analyzer. The content of each element of the carbon body is summarized in Table 3 below.

Sample N (atom. %) C (atom. %) H (atom. %) S (atom. %) SCN 59.27 32.16 2.42 1.66 SCNMg-850-H ₂ SO ₄ 1.60 88.60 0.52 0.55 SCNMg-850-HCl 1.66 87.24 0.53 0.41

6 and Table 3, it can be seen that the content of N and S elements in the SCN structure is reduced by acid leaching (acid washing) after magnesium thermal reduction. Meanwhile, in the acid leaching step, in order to confirm the effect on the elemental composition of the carbon body of the acid solution, the acid leaching was performed using 2M HCl to replace 0.5MH ₂ SO ₄ to prepare SCNMg-850-HCl, and as a result, S The elemental content was slightly reduced. These results suggest that trace amounts of H ₂ SO ₄ can be absorbed on the SCNMg-850 surface. 7 and 8, XPS analysis was performed to analyze the chemical state and composition of SCN and SCNmg-850. 7 (a) is a C 1s spectrum, (b) is an N 1s spectrum, (c) is an S 2p spectrum, FIG. 8 (a) is an O 1s spectrum of SCN, (b) is a SCNMg-850 O 1s Spectrum, Figure 7 (d) is a schematic diagram of SCN, Figure 7 (e) is a schematic diagram of S, N-doped graphene.

By analyzing the results of FIGS. 7 and 8, the chemical compositions of SCN and SCNMg-850 are summarized in Table 4 below.

Sample C 1s (at%) N 1s (at%) S 2p (at%) O 1s (at%) SCN 48.63 47.71 0.58 3.08 SCNMg-850 96.58 0.6 0.23 2.56

7, 8 and Table 4, the thermal reduction of magnesium reduces the content of N and S. In SCNmg-850, graphene-like sp2 carbon elements are arranged in a porous honeycomb structure, and N/S/O elements exist as sp2 C and CN/CS/CO species and π-π* excitations. and (see Fig. 7 (a)), pyridinic N, pyrrolic N, graphitic N, and N peaks of pyridinic N-oxide appear (see Fig. 7 (b)), CSC 2p 3/2 and CSC 2p An S peak of 1/2 appears, a sulfonic S peak such as a C-SOx-C moiety appears (see Fig. 7 (c)), and -OH groups and SOx ^2- peaks resulting from water molecules on the sample surface can be seen to appear.

Examples 4-6

(Production of electrode catalyst for fuel cell or water electrolysis reaction, SCNMg-X-YRh-Z)

100 mg of SCNMg-850 prepared in Example 2 was ultrasonically dispersed in 20 mL of a mixture (isopanol: water 1:1 volume ratio mixture), and RhCl ₃ .nH ₂ O (18 μM, 36 μM, and 73 μM RhCl 3 .nH 2 O (18 μM, 36 μM, and 73 μM RhCl ₃ .nH ₂ ) was dispersed in the dispersion. O, Examples 4-6) (RhCl ₃ .nH ₂ O (n=3.5) (Kojima chemicals co., ltd, 99.9%)) was added. Then, heat treatment was performed at 120° C. in an oil bath to evaporate all of the solvent. Subsequently, the obtained SCNMg-850-YRh (YRh means RhCl ₃ .nH ₂ O concentration Y μM) was washed with ethanol and water to remove unreacted metal ions, centrifuged at 14,000 rpm, and vacuum dried at 70 ° C. did The obtained SCNMg-850-YRh powder was heat-treated in an NH ₃ gas atmosphere (flow rate of 100 mL/min), at Z°C (500, 700 and 900°C, respectively), for 1 hour as an electrode catalyst (hereinafter, SCNMg-850-YRh) -Z) was prepared.

Comparative Examples 1-3

Reduced graphene oxide (hereinafter, denoted as rGO), commercially available Vulcan carbon XC-72 (Sigma Aldrich) (hereinafter denoted as VC), and SCN were prepared.

rGO was prepared by thermally reducing GO synthesized by the Hummer method at 850 °C for 2 hours in an Ar atmosphere.

Except for using the prepared rGO, VC, and SCN as a support to replace the SCNMg-850 of Example, proceed in the same manner as in the preparation of SCNMg-850-36Rh-500 of Example 5, Rh supported catalyst rGO-36Rh-500 , VC-36Rh-500, and SCN-36Rh-500 (Comparative Examples 1-3) were prepared.

[Evaluation Example 4] Synthesis of Rh-supported porous N and S double-doped carbon catalyst

Figure 9 (a) is the XRD analysis result of SCNMg-850-YRh-500, it can be confirmed whether or not Rh was successfully supported on the SCNMg-850 support. In FIG. 9, the peaks occurring at 2θ = 24° and 43° mean graphene, and the peaks occurring at 41.07°, 47.78° and 69.87° are (111), (200) and (220) crystal planes of cubic Rh. of high purity (JCPDS data No. 05-0685). From Fig. 9 (a), SCNMg-850-18Rh-500 and SCNMg-850-36Rh-500 do not show the above-mentioned Rh peak, and SCNMg-850-73Rh-500 shows the Rh crystal plane peak, Rh ^{3 +} It can be seen that not only the phase change according to the increase of the loading amount but also the particle size is increased.

From FIG. 9, TEM was measured to confirm the formation of Rh nanoparticles dispersed and supported on the SCNMg-850 support, and the SCNMg-850-36Rh-500 has a sheet-like structure with a uniform pore distribution, and a length of several hundred nm It can be seen that it is formed as (b of FIG. 9). In addition, from the results of high-angle annular dark-field scanning TEM (HAADF-STEM), it can be confirmed that SCNMg-850-36Rh-500 includes Rh clusters that are uniformly dispersed in the SCNMg-850 support ( Fig. 9 c). From the results of energy dispersive spectroscopy (EDS), it can be seen that C, N, S, Rh and O elements are uniformly dispersed ( FIG. 10 ). In addition, from the HR-TEM measurement results, it can be seen that SCNMg-850-36Rh-500 includes Rh clusters uniformly dispersed in the SCNMg-850 support, and the particle size of the Rh clusters is 1-3 nm ( Fig. 9 d). In the HR-TEM image magnified at high magnification, the boundary between the very small Rh nanoparticles and graphene is not clearly observed, which indicates that the surface elements of the Rh cluster are partially bound to the S and N elements of the graphene structure. (FIG. 9e). In the HR-TEM enlarged image of the red box region of FIG. 9d , the Rh cluster has a lattice distance of 0.221 nm, which coincides with the (111) plane of cubic Rh ( FIG. 9f ). However, when the content of RhCl ₃ .nH ₂ O is reduced (18 μM RhCl ₃ .nH ₂ O), the Rh particles tend to be non-uniformly dispersed ( FIGS. 11 a and b ), and conversely, RhCl ₃ .nH ₂ When the content of O is increased (73 μM RhCl ₃ .nH ₂ O), it can be seen that the Rh particle size is increased and partially aggregated ( FIGS. 11 c and d ).

[Evaluation Example 5] Electrochemical properties of Rh-supported N and S double-doped porous carbon catalyst

12A is a linear sweep voltammetry (LSV) graph for Examples (SCNMg-850-YRh-500, Y is 18, 36 and 73) and Comparative Examples (commercial Pt/C, Pt content of 20 wt% and 46 wt%). At this time, it was measured at a scan rate of 5 mV/sec in 1.0 M KOH. As a result, the HER performance of the SCNMg-850-36Rh-500 catalyst was the best. On the other hand, when referring to the TGA results, it can be seen that the Rh content of SCNMg-850-36Rh-500 is 5.2 wt%. (See FIG. 13) On the other hand, the SCNMg-850-36Rh-500 catalyst requires an overvoltage of 18 mV to have a current density of 10 mA/cm ² , but commercial Pt/C (Pt content 20wt% and 46wt%); A higher overvoltage (26 mV, 40 mV) is required.

Referring to FIG. 12B , electrode dynamics for H ⁺ reduction at an overpotential of 20 mV were analyzed by electrochemical impedance spectroscopy. SCNMg-850-36Rh-500 has significantly lower charge transfer resistance than commercial Pt/C, which means a fast faradaic process at the catalyst and electrolyte interface.

In addition, the loading amount and annealing temperature are one of the key factors in the electrocatalytic reaction. In order to analyze the effect of the annealing temperature on the HER performance of the electrocatalyst, the prepared SCNMg-850-36Rh sample was annealed at 500, 700 and 900° C. under NH ₃ gas flow, respectively. Referring to FIG. 12c , it can be seen that the HER performance of SCNMg-850-36Rh-500 is the highest. These results are analyzed to be influenced by the uniform distribution of ultra-small sized Rh clusters. This is because the uniform distribution of ultra-fine particles is known to be expressed with high electrocatalytic activity. In relation to this, compared to SCNMg-850-36Rh-500, in the case of SCNMg-850-36Rh-700 and SCNMg-850-36Rh-900, new peaks corresponding to 2θ degrees 40.010, 47.780, and 69.870 were generated according to XRD analysis. , which correspond to the (111), (200), and (220) crystal planes of Rh and are related to the Rh grain size (see FIG. 14 ). On the other hand, the same result can be confirmed through the TEM image (see FIG. 15). That is, when the annealing is performed at a temperature of 700° C. and 900° C. compared to 500° C., a new phase is formed, and Rh particles are aggregated to form particles having a relatively large size, thereby reducing the activity of the catalyst.

In addition, as described above, in the electrocatalyst system, the support (support) plays a very important role in the interaction with metal ions/nanoparticles. In order to evaluate the role of the scaffold, the HER performance of Examples (SCNMg-850-36Rh-500) and Comparative Examples 1 to 3 (rGO-36Rh-500, VC-36Rh-500, and SCN-36Rh-500) was compared. did Referring to FIG. 12d , from the LSV plot, the Example shows a higher HER activity than the comparative example, which is why SCNMg-850 has a sufficient number of electron-rich elements capable of binding to the vacant d-orbital of Rh. It is analyzed that this is because the active site is exposed to help uniform distribution of ultra-fine Rh nanoparticles. On the other hand, in Comparative Examples, large-sized Rh particles are non-uniformly distributed (see FIG. 16), and they exhibit a low specific surface area, multi-layered graphene, and low electrical conductivity (see FIG. 17). As a result, the electrocatalytic HER activity was low. On the contrary, SCNMg-850 forms graphene with a high specific surface area and 2 to 3 layers, and provides excellent electrical conductivity to contact the electrolyte using the maximum surface of the catalyst and has excellent charge transfer speed of the electrode, resulting in electrocatalytic HER activity This was excellent.

Therefore, referring to the Nyquist plot Fig. 12e, SCNMg-850-36Rh-500 has a higher charge transfer rate than VC-36Rh-500, rGO-36Rh-500, and SCN-36Rh-500, and a faster Faraday at the catalyst and electrolyte interface. You can see that the process is taking place. In addition, since the electrochemical active surface area (ECSA) is proportional to the double-layer capacitance of the catalyst, referring to the results of FIG. 18d , the SCNMg-850-36Rh-500 catalyst has a high electrochemically active surface area for H ⁺ adsorption/desorption It can be seen that provides

The conversion frequency (TOF, turn of frequency) of the catalyst was measured and shown in FIG. 12f. TOF results suggest that SCNMg-850-36Rh-500 can accommodate a higher amount of H ₂ s ^-1 compared to 46% Pt/C catalyst. These results indicate that the excellent catalytic activity can be attributed to the high availability of Rh species and its unique electronic structure and composition and overall properties. On the other hand, in order to confirm the composition and electronic structure of SCNMg-850-36Rh-500, X-ray photoelectron spectroscopy analysis (XPS) was performed. As a result of XPS analysis, C 96.53, S 0.17, N 1.08, Rh 0.28 and O 1.93 at% appear.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, but may be manufactured in a variety of different forms, and those of ordinary skill in the art to which the present invention pertains will appreciate the technical spirit of the present invention. However, it will be understood that the invention may be embodied in other specific forms without changing essential features. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive.

Claims (12)

preparing a bulk graphite-type polymer by polymerizing a precursor containing sulfur and nitrogen elements;
After mixing the bulk graphite-type polymer and the metal powder in an inert gas atmosphere, heat treatment at a temperature greater than or equal to the melting point of the metal; and
A method for producing a highly graphitic porous carbon body doped with sulfur and nitrogen, comprising the step of washing the heat treatment product with an acid. According to claim 1, wherein the sulfur and nitrogen element-containing precursor is at least one selected from the group consisting of thiourea, ammonium thiocyanate and thioacetamide, sulfur and nitrogen double doping high A method for producing a graphitic porous carbon body. The method of claim 1, wherein the sulfur- and nitrogen-containing precursor includes a sulfur-containing precursor and a nitrogen-containing precursor,
The sulfur-containing precursor is benzyl disulfide, thiophene, 2,2'-dithiophene, p-toluenesulfonic acid, and 2-thio It is an organic molecule precursor or a polymer precursor containing at least one selected from the group consisting of pinmethanol (2-thiophenemethanol),
The nitrogen-containing precursor is amino acids such as guanine, adenine, purine, melamine, urea, pyridine, aniline, dicyandiamide) , ethylenediamine (ethylenediamine) and ethylenediamine tetraacetic acid (EDTA) organic molecule or polymer precursor containing at least one selected from the group consisting of, sulfur and nitrogen double doping method for producing a highly graphitic porous carbon body. [Claim 2] The method of claim 1, wherein the metal powder is an alkaline earth metal powder, which is double doped with sulfur and nitrogen. The method of claim 1, wherein the bulk graphite-type polymer and the metal powder are mixed in an N+S:M atomic molar ratio of 1:0.3 to 1:5.
(The N and S are nitrogen and sulfur included as hetero elements in the bulk graphite polymer, respectively, M is a metal element of the metal powder, and N+S is the sum of the nitrogen and sulfur atoms) It contains 0.3 to 5.0 atomic % of N and 0.1 to 1.5 atomic % of S as a hetero element,
BET specific surface area of 80 ~ 1,000 m ² /g,
A porous sulfur and nitrogen double-doped highly graphitic carbon material satisfying the following Relations 1 and 2 in the intensity ratio of the peak measured by the Raman spectrum:
[Relational Expression 1]
0 ≤ I _D /I _G ≤ 0.95
[Relational Expression 2]
0.3 ≤ I _2D /I _G ≤ 2
In Relations 1 and 2, I _D is the peak intensity of the D band (near 1,350 cm ⁻¹ ) in the Raman spectrum, I _G is the peak intensity of the G band (near 1,580 cm ⁻¹ ) in the Raman spectrum, and I _2D is the Raman spectrum is the peak intensity of the 2D band (near 2,700 cm ^-1 ). [Claim 7] The carbon material of claim 6, wherein the carbon material is a porous sulfur and nitrogen double-doped highly graphitic carbon material satisfying the following relation:
[Relational Expression 3]
V ₁ /V ₂ ≤ 0.5
In Relation 3, V ₁ is the volume of micropores of the carbon body (cm ³ /g), and V ₂ is the volume of the mesopores of the carbon body (cm ³ /g). [Claim 7] The highly graphitic porous carbon body of claim 6, wherein the carbon body contains mesopores having a volume of 0.3 to 1.8 cm ³ /g. delete delete A fuel cell and/or water electrolysis reaction electrode catalyst comprising the highly graphitized porous carbon material doped with sulfur and nitrogen according to any one of claims 6 to 8. [Claim 12] The method of claim 11, wherein the sulfur and nitrogen double-doped highly graphitic porous carbon body is platinum (Pt), rhodium (Rh), nickel (Ni), cobalt (Co), iron (Fe), palladium ( Pd), copper (Cu), iridium (Ir), osmium (Os), molybdenum (Mo), vanadium (V), etc. or a combination thereof, characterized in that, for fuel cells and / or water electrolysis reaction electrode catalyst.

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