WO2021177705A1 - Single-atom catalyst and method for forming same - Google Patents

Single-atom catalyst and method for forming same Download PDF

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WO2021177705A1
WO2021177705A1 PCT/KR2021/002574 KR2021002574W WO2021177705A1 WO 2021177705 A1 WO2021177705 A1 WO 2021177705A1 KR 2021002574 W KR2021002574 W KR 2021002574W WO 2021177705 A1 WO2021177705 A1 WO 2021177705A1
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ceo
nanoparticles
ceria
forming
hollow
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Korean (ko)
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현택환
이병훈
이성찬
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서울대학교산학협력단
기초과학연구원
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    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
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    • B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
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    • B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
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    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/0009—Use of binding agents; Moulding; Pressing; Powdering; Granulating; Addition of materials ameliorating the mechanical properties of the product catalyst
    • B01J37/0018—Addition of a binding agent or of material, later completely removed among others as result of heat treatment, leaching or washing,(e.g. forming of pores; protective layer, desintegrating by heat)
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    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/0201—Impregnation
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B01J2523/00—Constitutive chemical elements of heterogeneous catalysts
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    • B01J2531/00—Additional information regarding catalytic systems classified in B01J31/00
    • B01J2531/30—Complexes comprising metals of Group III (IIIA or IIIB) as the central metal
    • B01J2531/37—Lanthanum
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    • B01J2531/00—Additional information regarding catalytic systems classified in B01J31/00
    • B01J2531/80—Complexes comprising metals of Group VIII as the central metal
    • B01J2531/82—Metals of the platinum group
    • B01J2531/824—Palladium

Definitions

  • the present invention relates to single atom catalysts and methods for their formation.
  • Single atom catalysts as a novel platform for heterogeneous catalysts have recently received a lot of attention.
  • Single atom catalysts consist of independent metal single atoms immobilized on various support surfaces.
  • One of the most important factors in the field of single atom catalysts is to define the metal atom composition and disperse the metal atoms on the support to improve the catalytic performance.
  • oxides are composed of more complex and arbitrary surface structures, it is difficult to disperse metal atoms.
  • the present invention provides single atom catalysts with excellent performance.
  • the present invention provides a method for forming the single atom catalyst.
  • a single atom catalyst according to embodiments of the present invention includes a ceria hollow nanoparticle and a metal atom loaded into the ceria hollow nanoparticle.
  • a method of forming a single atom catalyst according to embodiments of the present invention includes forming a sacrificial core, forming a ceria layer on the sacrificial core, loading a metal atom into the ceria layer, and sacrificing on the ceria layer forming a coating layer, heat-treating the ceria layer, and removing the sacrificial core and the sacrificial coating layer.
  • a single atom catalyst according to embodiments of the present invention may have excellent performance.
  • Figure 2 shows an image for each stage of formation of site-specific M/CeO 2 hollow nanoparticles.
  • a single atom catalyst according to embodiments of the present invention includes a ceria hollow nanoparticle and a metal atom loaded into the ceria hollow nanoparticle.
  • the hollow ceria nanoparticles may be composed of ceria grains of 10 nm or less.
  • the metal may include at least one of Pd, Rh, and Ru.
  • the single atom catalyst may have site specificity.
  • the metal atom may be located in the Ce pore of the hollow ceria nanoparticles.
  • a method of forming a single atom catalyst according to embodiments of the present invention includes forming a sacrificial core, forming a ceria layer on the sacrificial core, loading a metal atom into the ceria layer, and sacrificing on the ceria layer forming a coating layer, heat-treating the ceria layer, and removing the sacrificial core and the sacrificial coating layer.
  • the sacrificial core and the sacrificial coating layer may be formed of silica.
  • the metal atoms may be redistributed in the ceria layer by the heat treatment.
  • the metal atoms may be disposed in the Ce voids of the ceria layer.
  • the sacrificial coating layer may protect the ceria layer during the heat treatment.
  • the sacrificial core and the sacrificial coating layer may be removed to form hollow ceria nanoparticles.
  • the metal may include at least one of Pd, Rh, and Ru.
  • Spherical silica nanoparticles are formed by a sol-gel reaction. Add 0.86 mL of TEOS to a solution containing ethyl alcohol (23 mL), HO (4.3 mL) and aqueous ammonia (0.6 mL) at room temperature. The mixture is stirred vigorously for 6 hours. The reaction product was centrifuged, washed with water and ethanol, and dried at 65° C. for 2 hours.
  • 240 mg of dried silica powder is dispersed in 36 mL of ethylene glycol to form a first solution.
  • the first solution is sonicated for at least 10 minutes to obtain well-dispersed silica nanoparticles.
  • 1.8 mL of the second solution is added to the first solution, and the mixture is heated to 130° C. (3° C./min) for 15 hours.
  • the resulting pale yellow solution is centrifuged and washed three times with water.
  • SiO 2 @CeO 2 nanoparticles are dispersed in 40 mL of H 2 O.
  • Tetraaminepalladium(II) nitrate solution Pd(NH 3 ) 4 (NO 3 ) 2 , 10 wt % in H 2 O
  • the tetraaminepalladium(II) nitrate solution is diluted to 0.4 wt%, and 1 mL is added to a 40 mL colloidal solution of SiO 2 @CeO 2 nanoparticles.
  • Rh atom adsorption 40 mg of rhodium(III) chloride is dissolved in 10 mL of H 2 O, and then 1 mL is added to a 40 mL colloidal solution of SiO 2 @CeO 2 nanoparticles.
  • Ru atom adsorption 0.05 mL of hydrochloric acid is added to change the surface charge of SiO 2 nanoparticles.
  • the SiO 2 @M/CeO 2 nanoparticles are dispersed in 40 mL of H 2 O. After adding 0.4 g of PVP, the solution was stirred overnight to adsorb PVP to the surface of SiO 2 @M/CeO 2 nanoparticles. After PVP adsorption, the product is centrifuged and redispersed by sonication in a solution of ethanol (32 mL) and H 2 O (6 mL) for 10 min. Add 1.2 mL of TEOS and 0.84 mL of aqueous ammonia to the solution. Immediate stabilization of metal atoms adsorbed on the surface causes rapid color change within 10 seconds, and a silica overlayer (coating layer) is formed. After 4 hours of reaction, the resulting nanoparticles are centrifuged and washed with ethanol. The product is dried in an electric oven at 80° C. for 3 hours.
  • the dried SiO 2 @M/CeO 2 @SiO 2 powder is calcined at 900° C. for 2 hours.
  • Annealing heat treatment
  • the silica overlayer coating layer may protect CeO 2 .
  • SiO 2 etching For SiO 2 etching, calcined SiO 2 @M/CeO2@SiO 2 nanoparticles are dispersed in 75 mL of 1M NaOH solution. The solution is heated to 90° C. with continuous stirring. After 6 hours, the product is centrifuged and washed with H 2 O to obtain M/CeO 2 hollow nanoparticles. The product is dried overnight at 80° C. in an electric oven.
  • a pure CeO 2 sample was prepared without a metal atom adsorption process in the same manner as for M/CeO 2 described above.
  • Pd IMP /CeO 2 is formed according to a conventional impregnation method. 300 mg of cerium (IV) oxide (CeO 2 ) is dispersed in 40 mL of H 2 O. For Pd atom adsorption, add 0.4 wt% tetraaminepalladium(II) nitrate solution to 40 mL colloidal solution. The mixed colloidal solution is vigorously stirred at room temperature for 3 hours. After stirring, the product is centrifuged, washed with water and dried at 80° C. overnight. Calcined at 900° C. for 2 hours.
  • FIG. 1 shows a method of forming a site-specific M/CeO 2 hollow nanoparticles (single atom catalyst)
  • FIG. 2 shows an image for each stage of formation of a site-specific M/CeO 2 hollow nanoparticles
  • FIG. 3 is a silica over Shows the image of the CeO 2 surface according to the reaction time of the layer coating
  • FIG. 4 shows the image of Pd/CeO 2 nanoparticles according to the silica etching time
  • FIG. 5 shows the HRTEM image and SAED pattern of the Pd/CeO 2 nanoparticles indicates.
  • a modified lab-bake-fill process was used, which prevents surface diffusion and deposits metal atoms only in Ce vacancies, which are the most stable in CeO 2 . and coating with a silica overlayer to allow for the high temperature heat treatment necessary for incorporation.
  • the modified wrap-bake-peel process is 1) CeO 2 coating on SiO 2 spheres, followed by adsorption of metal precursors, 2) coating (wrap) with SiO 2 overlayer, 3) heat treatment at 900° C. to induce thermodynamic redistribution (bake), 4) etching (fill) of the SiO 2 layer.
  • FIG. 6 shows a TEM image of Pd/CeO 2 hollow nanoparticles
  • FIG. 7 shows the XRD patterns of pure CeO 2 nanoparticles and Pd/CeO 2 hollow nanoparticles
  • FIG. 8 shows the k of Pd/CeO 2 hollow nanoparticles. Shows the Fourier transform of the 3- weighted EXAFS spectrum
  • FIG. 9 shows a TEM image of Pd IMP /CeO 2 nanoparticles prepared by the impregnation method without a silica overlayer
  • FIG. 10 shows pure CeO 2 nanoparticles and Pd IMP /CeO 2 Shows the XRD pattern of nanoparticles
  • the Pd K edge spectrum in EXAFS (extended X-ray absorption fine structure) analysis shows the presence of two characteristic distances of Pd-O and Pd-Ce on crystalline fluorite (FIG. 8).
  • No characteristic peak corresponding to the Pd-Pd metal bond is observed, which is evidenced by the XRD data. This indicates that the Pd atoms are located exclusively at the Ce site.
  • the site-specific configuration results in a main peak corresponding to the direct bonding of Pd atoms and lattice oxygen (Pd-O), as well as a small peak representing the local CeO 2 environment (Pd-Ce) around the isolated Pd.
  • EXAFS curve fitting analysis allows the investigation of the local coordination environment. The best-fitting curve shows that the first peak originates from the first Pd-O shell configuration while the small second peak originates from the Pd-Ce second shell configuration (Fig. 8).
  • Table 1 summarizes the EXAFS fitting of M/CeO 2 hollow nanoparticles
  • Table 2 shows the concentration of atoms in M/CeO 2 hollow nanoparticles measured by ICP-AES.
  • FIG. 11 shows the XRD patterns of pure CeO 2 nanoparticles and various M/CeO 2 hollow nanoparticles
  • FIG. 12 shows TEM images (low-magnification) of various M/CeO 2 hollow nanoparticles ((a) Pd, (b) Rh, (c) Ru)
  • FIG. 13 shows TEM images (high-magnification) of various M/CeO 2 hollow nanoparticles ((a) Pd, (b) Rh, (c) Ru).
  • 14 shows STEM-EDS elemental mapping data of various M/CeO 2 hollow nanoparticles ((a) Pd, (b) Rh, (c) Ru)
  • FIG. 15 is various M/CeO 2 hollow nanoparticles.
  • FIG. 16 is k 3 -weighted EXAFS spectrum of various M/CeO 2 hollow nanoparticles shows the Fourier transform of ((a) Pd, (b) Rh, (c) Ru).
  • Pd/CeO 2 hollow nanoparticles were found to be very effective catalysts for Suzuki coupling. It has a particularly high selectivity (TOF > 160h ⁇ 1 , selectivity >97%). Pd IMP /CeO 2 nanoparticles show much lower selectivity (about 80%), so the high selectivity of Pd/CeO 2 hollow nanoparticles appears to originate from their exclusively active sites. Pure CeO 2 nanoparticles were inactive in this reaction, and Pd/C (5 wt.%) was also almost inactive. As a result, Pd/CeO 2 hollow nanoparticles outperformed all investigated heterogeneous catalysts and showed similar performance to homogeneous Pd(OAc) 2 catalysts.
  • the Pd/CeO 2 hollow nanoparticles showed no apparent deactivation of the catalyst performance even after 5 cycles because the TOF and selectivity during each cycle remained constant at values greater than about 160 h ⁇ 1 and 97%, respectively. .
  • a single atom catalyst according to embodiments of the present invention may have excellent performance.

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Abstract

A single-atom catalyst and a method for forming same are provided. The single-atom catalyst comprises hollow ceria nanoparticles and a metal atom loaded on the hollow ceria nanoparticles. The method for forming the single-atom catalyst comprises the steps of: forming a sacrificial core; forming a ceria layer on the sacrificial core; loading a metal atom on the ceria layer; forming a sacrificial coating layer on the ceria layer; heat-treating the ceria layer; and removing the sacrificial core and the sacrificial coating layer.

Description

단일 원자 촉매 및 그 형성 방법Single atom catalyst and method for its formation
본 발명은 단일 원자 촉매 및 그 형성 방법에 관한 것이다.FIELD OF THE INVENTION The present invention relates to single atom catalysts and methods for their formation.
불균일 촉매의 새로운 플랫폼으로 단일 원자 촉매(single atom catalysts)는 최근 많은 관심을 받고 있다. 단일 원자 촉매는 다양한 지지체 표면에 고정된 독립된 금속 단일 원자로 구성된다.Single atom catalysts as a novel platform for heterogeneous catalysts have recently received a lot of attention. Single atom catalysts consist of independent metal single atoms immobilized on various support surfaces.
단일 원자 촉매 분야에서 가장 중요한 요소 중 하나는 촉매 성능을 향상시키기 위해 금속 원자 구성을 정의하고 지지체 상에 금속 원자를 분산시키는 것이다. 그러나, 산화물은 보다 복잡하고 임의적인 표면 구조로 구성되어 있기 때문에 금속 원자를 분산시키기가 어렵다.One of the most important factors in the field of single atom catalysts is to define the metal atom composition and disperse the metal atoms on the support to improve the catalytic performance. However, since oxides are composed of more complex and arbitrary surface structures, it is difficult to disperse metal atoms.
본 발명은 우수한 성능을 갖는 단일 원자 촉매를 제공한다.The present invention provides single atom catalysts with excellent performance.
본 발명은 상기 단일 원자 촉매의 형성 방법을 제공한다.The present invention provides a method for forming the single atom catalyst.
본 발명의 다른 목적들은 다음의 상세한 설명과 첨부한 도면으로부터 명확해 질 것이다.Other objects of the present invention will become apparent from the following detailed description and accompanying drawings.
본 발명의 실시예들에 따른 단일 원자 촉매는, 세리아 중공 나노입자 및 상기 세리아 중공 나노입자에 로딩된 금속 원자를 포함한다.A single atom catalyst according to embodiments of the present invention includes a ceria hollow nanoparticle and a metal atom loaded into the ceria hollow nanoparticle.
본 발명의 실시예들에 따른 단일 원자 촉매의 형성 방법은, 희생 코어를 형성하는 단계, 상기 희생 코어 위에 세리아 층을 형성하는 단계, 상기 세리아 층에 금속 원자를 로딩하는 단계, 상기 세리아 층 위에 희생 코팅층을 형성하는 단계, 상기 세리아 층을 열처리하는 단계, 및 상기 희생 코어 및 상기 희생 코팅층을 제거하는 단계를 포함한다.A method of forming a single atom catalyst according to embodiments of the present invention includes forming a sacrificial core, forming a ceria layer on the sacrificial core, loading a metal atom into the ceria layer, and sacrificing on the ceria layer forming a coating layer, heat-treating the ceria layer, and removing the sacrificial core and the sacrificial coating layer.
본 발명의 실시예들에 따른 단일 원자 촉매는 우수한 성능을 가질 수 있다.A single atom catalyst according to embodiments of the present invention may have excellent performance.
도 1은 사이트 특이적 M/CeO2 중공 나노입자(단일 원자 촉매)의 형성 방법을 나타낸다.1 shows a method for forming site-specific M/CeO 2 hollow nanoparticles (single atom catalyst).
도 2는 사이트 특이적 M/CeO2 중공 나노입자의 형성 단계 별 이미지를 나타낸다.Figure 2 shows an image for each stage of formation of site-specific M/CeO 2 hollow nanoparticles.
도 3은 실리카 오버레이어 코팅의 반응 시간에 따른 CeO2 표면의 이미지를 나타낸다.3 shows an image of the CeO 2 surface according to the reaction time of the silica overlayer coating.
도 4는 실리카 에칭 시간에 따른 Pd/CeO2 나노입자의 이미지를 나타낸다.4 shows an image of Pd/CeO 2 nanoparticles as a function of silica etching time.
도 5는 Pd/CeO2 나노입자의 HRTEM 이미지 및 SAED 패턴을 나타낸다.5 shows the HRTEM image and SAED pattern of Pd/CeO 2 nanoparticles.
도 6은 Pd/CeO2 중공 나노입자의 TEM 이미지를 나타낸다.6 shows a TEM image of Pd/CeO 2 hollow nanoparticles.
도 7은 순수 CeO2 나노입자 및 Pd/CeO2 중공 나노입자의 XRD 패턴을 나타낸다.7 shows the XRD patterns of pure CeO 2 nanoparticles and Pd/CeO 2 hollow nanoparticles.
도 8은 Pd/CeO2 중공 나노입자의 k3-weighted EXAFS 스펙트럼의 푸리에 변환을 나타낸다.8 shows the Fourier transform of the k 3 -weighted EXAFS spectrum of the Pd/CeO 2 hollow nanoparticles.
도 9는 실리카 오버레이어 없이 함침법으로 제조된 PdIMP/CeO2 나노입자의 TEM 이미지를 나타낸다.9 shows a TEM image of Pd IMP /CeO 2 nanoparticles prepared by the impregnation method without a silica overlayer.
도 10은 순수 CeO2 나노입자 및 PdIMP/CeO2 나노입자의 XRD 패턴을 나타낸다.10 shows the XRD patterns of pure CeO 2 nanoparticles and Pd IMP /CeO 2 nanoparticles.
도 11은 순수 CeO2 나노입자 및 다양한 M/CeO2 중공 나노입자의 XRD 패턴을 나타낸다.11 shows the XRD patterns of pure CeO 2 nanoparticles and various M/CeO 2 hollow nanoparticles.
도 12는 다양한 M/CeO2 중공 나노입자의 TEM 이미지(low-magnification)를 나타낸다((a) Pd, (b) Rh, (c) Ru).12 shows TEM images (low-magnification) of various M/CeO 2 hollow nanoparticles ((a) Pd, (b) Rh, (c) Ru).
도 13은 다양한 M/CeO2 중공 나노입자의 TEM 이미지(high-magnification)를 나타낸다((a) Pd, (b) Rh, (c) Ru).13 shows TEM images (high-magnification) of various M/CeO 2 hollow nanoparticles ((a) Pd, (b) Rh, (c) Ru).
도 14는 다양한 M/CeO2 중공 나노입자의 STEM-EDS 원소 맵핑(elemental mapping) 데이터를 나타낸다((a) Pd, (b) Rh, (c) Ru).14 shows STEM-EDS elemental mapping data of various M/CeO 2 hollow nanoparticles ((a) Pd, (b) Rh, (c) Ru).
도 15는 다양한 M/CeO2 중공 나노입자의 k3-weighted EXAFS 스펙트럼의 역푸리에 변환을 나타낸다((a) Pd, (b) Rh, (c) Ru).15 shows the inverse Fourier transform of k 3 -weighted EXAFS spectra of various M/CeO 2 hollow nanoparticles ((a) Pd, (b) Rh, (c) Ru).
도 16은 다양한 M/CeO2 중공 나노입자의 k3-weighted EXAFS 스펙트럼의 푸리에 변환을 나타낸다((a) Pd, (b) Rh, (c) Ru).16 shows Fourier transforms of k 3 -weighted EXAFS spectra of various M/CeO 2 hollow nanoparticles ((a) Pd, (b) Rh, (c) Ru).
도 17은 스즈키 커플링에 대한 Pd/CeO2 중공 나노입자의 안정성 테스트 결과를 나타낸다.17 shows the stability test results of Pd/CeO 2 hollow nanoparticles for Suzuki coupling.
도 18은 촉매 테스트 전후의 Pd/CeO2 중공 나노입자의 TEM 이미지를 나타낸다((a) 테스트 전, (b) 5회 테스트 후). 18 shows TEM images of Pd/CeO 2 hollow nanoparticles before and after the catalyst test ((a) before the test, (b) after 5 tests).
이하, 실시예들을 통하여 본 발명을 상세하게 설명한다. 본 발명의 목적, 특징, 장점은 이하의 실시예들을 통해 쉽게 이해될 것이다. 본 발명은 여기서 설명되는 실시예들에 한정되지 않고, 다른 형태로 구체화될 수도 있다. 여기서 소개되는 실시예들은 개시된 내용이 철저하고 완전해질 수 있도록 그리고 본 발명이 속하는 기술 분야에서 통상의 지식을 가진 자에게 본 발명의 사상이 충분히 전달될 수 있도록 하기 위해 제공되는 것이다. 따라서, 이하의 실시예들에 의하여 본 발명이 제한되어서는 안 된다.Hereinafter, the present invention will be described in detail through examples. Objects, features and advantages of the present invention will be easily understood through the following examples. The present invention is not limited to the embodiments described herein, and may be embodied in other forms. The embodiments introduced herein are provided so that the disclosed content can be thorough and complete, and the spirit of the present invention can be sufficiently conveyed to those of ordinary skill in the art to which the present invention pertains. Therefore, the present invention should not be limited by the following examples.
본 발명의 실시예들에 따른 단일 원자 촉매는, 세리아 중공 나노입자 및 상기 세리아 중공 나노입자에 로딩된 금속 원자를 포함한다.A single atom catalyst according to embodiments of the present invention includes a ceria hollow nanoparticle and a metal atom loaded into the ceria hollow nanoparticle.
상기 세리아 중공 나노입자는 10nm 이하의 세리아 그레인으로 구성될 수 있다. The hollow ceria nanoparticles may be composed of ceria grains of 10 nm or less.
상기 금속은 Pd, Rh, 및 Ru 중에서 적어도 하나를 포함할 수 있다.The metal may include at least one of Pd, Rh, and Ru.
상기 단일 원자 촉매는 사이트 특이성을 가질 수 있다.The single atom catalyst may have site specificity.
상기 금속 원자는 상기 세리아 중공 나노입자의 Ce 공극에 위치할 수 있다.The metal atom may be located in the Ce pore of the hollow ceria nanoparticles.
본 발명의 실시예들에 따른 단일 원자 촉매의 형성 방법은, 희생 코어를 형성하는 단계, 상기 희생 코어 위에 세리아 층을 형성하는 단계, 상기 세리아 층에 금속 원자를 로딩하는 단계, 상기 세리아 층 위에 희생 코팅층을 형성하는 단계, 상기 세리아 층을 열처리하는 단계, 및 상기 희생 코어 및 상기 희생 코팅층을 제거하는 단계를 포함한다.A method of forming a single atom catalyst according to embodiments of the present invention includes forming a sacrificial core, forming a ceria layer on the sacrificial core, loading a metal atom into the ceria layer, and sacrificing on the ceria layer forming a coating layer, heat-treating the ceria layer, and removing the sacrificial core and the sacrificial coating layer.
상기 희생 코어 및 상기 희생 코팅층은 실리카로 형성될 수 있다.The sacrificial core and the sacrificial coating layer may be formed of silica.
상기 열처리에 의해 상기 금속 원자는 상기 세리아 층에서 재분포될 수 있다.The metal atoms may be redistributed in the ceria layer by the heat treatment.
상기 열처리에 의해 상기 금속 원자는 상기 세리아 층의 Ce 공극에 배치될 수 있다. By the heat treatment, the metal atoms may be disposed in the Ce voids of the ceria layer.
상기 희생 코팅층은 상기 열처리 동안 상기 세리아 층을 보호할 수 있다.The sacrificial coating layer may protect the ceria layer during the heat treatment.
상기 희생 코어 및 상기 희생 코팅층이 제거되어 세리아 중공 나노입자가 형성될 수 있다.The sacrificial core and the sacrificial coating layer may be removed to form hollow ceria nanoparticles.
상기 금속은 Pd, Rh, 및 Ru 중에서 적어도 하나를 포함할 수 있다.The metal may include at least one of Pd, Rh, and Ru.
[실시예] M/CeO2 중공 나노입자[Example] M/CeO 2 Hollow Nanoparticles
1) 실리카 나노입자(SiO2 NP) 형성1) Formation of silica nanoparticles (SiO 2 NP)
구형 실리카 나노입자는 졸-겔 반응에 의해 형성된다. TEOS 0.86mL를 실온에서 에틸 알코올(23mL), H2O(4.3mL) 및 수성 암모니아(0.6mL)를 포함하는 용액에 첨가한다. 이 혼합물을 6시간 동안 격렬하게 교반한다. 반응 생성물을 원심 분리하여 물 및 에탄올로 세척하고 65℃에서 2시간 동안 건조시킨다.Spherical silica nanoparticles are formed by a sol-gel reaction. Add 0.86 mL of TEOS to a solution containing ethyl alcohol (23 mL), HO (4.3 mL) and aqueous ammonia (0.6 mL) at room temperature. The mixture is stirred vigorously for 6 hours. The reaction product was centrifuged, washed with water and ethanol, and dried at 65° C. for 2 hours.
2) 실리카(SiO2) 나노입자를 CeO2로 코팅(SiO2@CeO2 나노입자)2) Coating silica (SiO 2 ) nanoparticles with CeO 2 (SiO 2 @CeO 2 nanoparticles)
240mg의 건조된 실리카 분말을 36mL의 에틸렌 글리콜에 분산시켜 제1 용액을 형성한다. 상기 제1 용액을 10분 이상 초음파 처리하여 잘 분산된 실리카 나노입자를 얻는다. 질산 세륨 6 수화물 3g을 6.22mL의 H2O에 용해시켜 제2 용액을 형성한다. 상기 제2 용액 1.8mL를 상기 제1 용액에 첨가하고, 이 혼합물을 15시간 동안 130℃(3℃/분)로 가열한다. 생성된 담황색 용액을 원심 분리하고 물로 3회 세척한다. 마지막으로, SiO2@CeO2 나노입자를 40mL의 H2O에 분산시킨다.240 mg of dried silica powder is dispersed in 36 mL of ethylene glycol to form a first solution. The first solution is sonicated for at least 10 minutes to obtain well-dispersed silica nanoparticles. Dissolve 3 g of cerium nitrate hexahydrate in 6.22 mL of H 2 O to form a second solution. 1.8 mL of the second solution is added to the first solution, and the mixture is heated to 130° C. (3° C./min) for 15 hours. The resulting pale yellow solution is centrifuged and washed three times with water. Finally, SiO 2 @CeO 2 nanoparticles are dispersed in 40 mL of H 2 O.
3) SiO2@CeO2 나노입자에 금속 원자(M) 흡착(SiO2@M/CeO2)3) Adsorption of metal atoms (M) to SiO 2 @CeO 2 nanoparticles (SiO 2 @M/CeO 2 )
테트라아민팔라듐(II) 나이트레이트 용액(Pd(NH3)4(NO3)2, H2O 중 10wt%), 로듐 클로라이드 하이드레이트(RhCl3·xH2O, 순도=99.98%) 및 포타시움 헥사클로로루테네이트(K2RuCl6, 순도=99.95 %)는 금속 전구체로 사용된다. Tetraaminepalladium(II) nitrate solution (Pd(NH 3 ) 4 (NO 3 ) 2 , 10 wt % in H 2 O), rhodium chloride hydrate (RhCl 3 .xH 2 O, purity=99.98%) and potassium hexachloro Ruthenate (K 2 RuCl 6 , purity=99.95%) is used as a metal precursor.
Pd 원자 흡착을 위해, 테트라아민팔라듐(II) 나이트레이트 용액을 0.4wt%로 희석하고, 1mL를 SiO2@CeO2 나노입자의 40mL 콜로이드 용액에 첨가한다. Rh 원자 흡착을 위해, 40mg의 로듐(III) 클로라이드를 10mL의 H2O에 용해시킨 후, 1mL를 SiO2@CeO2 나노입자의 40mL 콜로이드 용액에 첨가한다다. Ru 원자 흡착을 위해, 0.05mL의 염산을 첨가하여 SiO2 나노입자의 표면 전하를 변경시킨다. 포타시움 헥사클로로루테네이트(IV) 40mg을 10mL의 H2O에 용해시킨 후, 1mL를 SiO2@CeO2 나노입자의 40mL 콜로이드 용액에 첨가한다. 상기 전구체의 양은 최종 생성물에서 금속 원자의 약 1wt% 로딩에 해당한다. 혼합된 콜로이드 용액을 실온에서 3시간 동안 격렬하게 교반한다. 교반 후 생성물(SiO2@M/CeO2)을 원심 분리하고 물로 세척한다. 금속 이온 흡착은 생성물(SiO2@M/CeO2)의 색상을 연황색에서 흡착된 금속 이온의 색상(Pd-황색; Rh-적색; Ru-진한 녹색)으로 변경시킨다.For Pd atom adsorption, the tetraaminepalladium(II) nitrate solution is diluted to 0.4 wt%, and 1 mL is added to a 40 mL colloidal solution of SiO 2 @CeO 2 nanoparticles. For Rh atom adsorption, 40 mg of rhodium(III) chloride is dissolved in 10 mL of H 2 O, and then 1 mL is added to a 40 mL colloidal solution of SiO 2 @CeO 2 nanoparticles. For Ru atom adsorption, 0.05 mL of hydrochloric acid is added to change the surface charge of SiO 2 nanoparticles. 40 mg of potassium hexachlororuthenate (IV) is dissolved in 10 mL of H 2 O, and then 1 mL is added to a 40 mL colloidal solution of SiO 2 @CeO 2 nanoparticles. The amount of the precursor corresponds to about 1 wt % loading of metal atoms in the final product. The mixed colloidal solution is vigorously stirred at room temperature for 3 hours. After stirring, the product (SiO 2 @M/CeO 2 ) is centrifuged and washed with water. Metal ion adsorption changes the color of the product (SiO 2 @M/CeO 2 ) from light yellow to the color of the adsorbed metal ions (Pd-yellow; Rh-red; Ru-dark green).
4) SiO2@M/CeO2 나노입자를 실리카(SiO2)로 코팅(SiO2@M/CeO2@SiO2 나노입자): 랩 공정(Wrap process)4) Coating SiO 2 @M/CeO 2 nanoparticles with silica (SiO 2 ) (SiO 2 @M/CeO 2 @SiO 2 nanoparticles): Wrap process
상기 SiO2@M/CeO2 나노입자를 40mL의 H2O에 분산시킨다. 0.4g의 PVP를 첨가한 후 용액을 밤새 교반하여 SiO2@M/CeO2 나노입자의 표면에 PVP를 흡착시킨다. PVP 흡착 후 생성물을 원심 분리하고 에탄올(32mL) 및 H2O(6mL)의 용액에 10분 동안 초음파 처리하여 재분산시킨다. 1.2mL의 TEOS 및 0.84mL의 수성 암모니아를 상기 용액에 첨가한다. 표면에 흡착된 금속 원자의 즉각적인 안정화는 10초 이내에 빠른 색 변화를 일으키고, 실리카 오버레이어(코팅층)가 형성된다. 반응 4시간 후 생성된 나노입자를 원심 분리하고 에탄올로 세척한다. 생성물을 전기 오븐에서 80℃에서 3시간 동안 건조시킨다.The SiO 2 @M/CeO 2 nanoparticles are dispersed in 40 mL of H 2 O. After adding 0.4 g of PVP, the solution was stirred overnight to adsorb PVP to the surface of SiO 2 @M/CeO 2 nanoparticles. After PVP adsorption, the product is centrifuged and redispersed by sonication in a solution of ethanol (32 mL) and H 2 O (6 mL) for 10 min. Add 1.2 mL of TEOS and 0.84 mL of aqueous ammonia to the solution. Immediate stabilization of metal atoms adsorbed on the surface causes rapid color change within 10 seconds, and a silica overlayer (coating layer) is formed. After 4 hours of reaction, the resulting nanoparticles are centrifuged and washed with ethanol. The product is dried in an electric oven at 80° C. for 3 hours.
5) SiO2@M/CeO2@SiO2 나노입자에서 금속 원자의 열역학적 재분포: 베이크 공정(Bake process)5) Thermodynamic redistribution of metal atoms in SiO 2 @M/CeO 2 @SiO 2 nanoparticles: Bake process
금속 원자의 재분포를 공간적으로 한정하기 위해, 건조된 SiO2@M/CeO2@SiO2 분말을 900℃에서 2시간 동안 하소시킨다. 재분포 공정에 충분한 산소를 공급하기 위해 어닐링(열처리)을 야외에서 수행한다. 베이크 공정에서 어닐링이 수행되는 동안 실리카 오버레이어(코팅층)가 CeO2를 보호할 수 있다.To spatially confine the redistribution of metal atoms, the dried SiO 2 @M/CeO 2 @SiO 2 powder is calcined at 900° C. for 2 hours. Annealing (heat treatment) is performed outdoors to supply sufficient oxygen to the redistribution process. During annealing in the bake process, the silica overlayer (coating layer) may protect CeO 2 .
6) 실리카(SiO2)를 에칭하여 M/CeO2 중공 나노입자 형성(M/CeO2 중공 나노입자): 필 공정(Peel process)6) Etching silica (SiO 2 ) to form M/CeO 2 hollow nanoparticles (M/CeO 2 hollow nanoparticles): Peel process
SiO2 에칭을 위해 하소된 SiO2@M/CeO2@SiO2 나노입자를 75mL의 1M NaOH 용액에 분산시킨다. 용액을 연속 교반하면서 90℃로 가열한다. 6시간 후 생성물을 원심 분리하고 H2O로 세척하여 M/CeO2 중공 나노입자를 얻는다. 생성물을 전기 오븐에서 80℃에서 밤새 건조시킨다.For SiO 2 etching, calcined SiO 2 @M/CeO2@SiO 2 nanoparticles are dispersed in 75 mL of 1M NaOH solution. The solution is heated to 90° C. with continuous stirring. After 6 hours, the product is centrifuged and washed with H 2 O to obtain M/CeO 2 hollow nanoparticles. The product is dried overnight at 80° C. in an electric oven.
[비교예 1] 금속 원자 흡착이 없는 순수 CeO2 [Comparative Example 1] Pure CeO 2 without metal atom adsorption
순수한 CeO2 샘플은 상기한 M/CeO2와 동일한 방식으로 금속 원자 흡착 공정없이 제조된다.A pure CeO 2 sample was prepared without a metal atom adsorption process in the same manner as for M/CeO 2 described above.
[비교예 2] 함침법에 의해 실리카층 없이 제조된 PdIMP/CeO2 [Comparative Example 2] Pd IMP /CeO 2 prepared without a silica layer by the impregnation method
PdIMP/CeO2는 종래의 함침법에 따라 형성된다. 300mg의 세륨(IV) 산화물(CeO2)을 40mL의 H2O에 분산시킨다. Pd 원자 흡착의 경우, 0.4wt% 테트라아민팔라듐(II) 나이트레이트 용액을 40mL 콜로이드 용액에 첨가한다. 혼합된 콜로이드 용액을 실온에서 3시간 동안 격렬하게 교반한다. 교반 후 생성물을 원심 분리하고 물로 세척한 다음 80℃에서 밤새 건조시킨다. 900℃에서 2시간 동안 하소시킨다.Pd IMP /CeO 2 is formed according to a conventional impregnation method. 300 mg of cerium (IV) oxide (CeO 2 ) is dispersed in 40 mL of H 2 O. For Pd atom adsorption, add 0.4 wt% tetraaminepalladium(II) nitrate solution to 40 mL colloidal solution. The mixed colloidal solution is vigorously stirred at room temperature for 3 hours. After stirring, the product is centrifuged, washed with water and dried at 80° C. overnight. Calcined at 900° C. for 2 hours.
도 1은 사이트 특이적 M/CeO2 중공 나노입자(단일 원자 촉매)의 형성 방법을 나타내고, 도 2는 사이트 특이적 M/CeO2 중공 나노입자의 형성 단계 별 이미지를 나타내고, 도 3은 실리카 오버레이어 코팅의 반응 시간에 따른 CeO2 표면의 이미지를 나타내고, 도 4는 실리카 에칭 시간에 따른 Pd/CeO2 나노입자의 이미지를 나타내며, 도 5는 Pd/CeO2 나노입자의 HRTEM 이미지 및 SAED 패턴을 나타낸다.1 shows a method of forming a site-specific M/CeO 2 hollow nanoparticles (single atom catalyst), FIG. 2 shows an image for each stage of formation of a site-specific M/CeO 2 hollow nanoparticles, and FIG. 3 is a silica over Shows the image of the CeO 2 surface according to the reaction time of the layer coating, FIG. 4 shows the image of Pd/CeO 2 nanoparticles according to the silica etching time, and FIG. 5 shows the HRTEM image and SAED pattern of the Pd/CeO 2 nanoparticles indicates.
도 1 내지 도 5를 참조하면, 사이트 특이 단일 원자 촉매의 합성을 위해, 변형된 랩-베이크-필 공정이 사용되었고, 이 공정은 표면 확산을 방지하고 CeO2에서 가장 안정적인 Ce 공극에만 금속 원자를 포함시키는데 필요한 고온 열처리를 허용하는 실리카 오버레이어로 코팅하는 것을 포함한다. 변형된 랩-베이킹-필 공정은 1) SiO2 구체에 CeO2 코팅, 이어서 금속 전구체의 흡착, 2) SiO2 오버레이어로 코팅(랩), 3) 열역학적 재분포를 유도하기 위해 900℃에서 열처리(베이크), 4) SiO2층의 에칭(필)을 포함한다.1 to 5 , for the synthesis of the site-specific single-atom catalyst, a modified lab-bake-fill process was used, which prevents surface diffusion and deposits metal atoms only in Ce vacancies, which are the most stable in CeO 2 . and coating with a silica overlayer to allow for the high temperature heat treatment necessary for incorporation. The modified wrap-bake-peel process is 1) CeO 2 coating on SiO 2 spheres, followed by adsorption of metal precursors, 2) coating (wrap) with SiO 2 overlayer, 3) heat treatment at 900° C. to induce thermodynamic redistribution (bake), 4) etching (fill) of the SiO 2 layer.
도 6은 Pd/CeO2 중공 나노입자의 TEM 이미지를 나타내고, 도 7은 순수 CeO2 나노입자 및 Pd/CeO2 중공 나노입자의 XRD 패턴을 나타내고, 도 8은 Pd/CeO2 중공 나노입자의 k3-weighted EXAFS 스펙트럼의 푸리에 변환을 나타내고, 도 9는 실리카 오버레이어 없이 함침법으로 제조된 PdIMP/CeO2 나노입자의 TEM 이미지를 나타내며, 도 10은 순수 CeO2 나노입자 및 PdIMP/CeO2 나노입자의 XRD 패턴을 나타낸다6 shows a TEM image of Pd/CeO 2 hollow nanoparticles, FIG. 7 shows the XRD patterns of pure CeO 2 nanoparticles and Pd/CeO 2 hollow nanoparticles, and FIG. 8 shows the k of Pd/CeO 2 hollow nanoparticles. Shows the Fourier transform of the 3- weighted EXAFS spectrum, FIG. 9 shows a TEM image of Pd IMP /CeO 2 nanoparticles prepared by the impregnation method without a silica overlayer, and FIG. 10 shows pure CeO 2 nanoparticles and Pd IMP /CeO 2 Shows the XRD pattern of nanoparticles
도 6 내지 도 10을 참조하면, 저해상도 및 고해상도 투과 전자 현미경(HRTEM) 이미지는 잘 분산된 Pd/CeO2 중공 나노입자가 10nm 이하(예를 들어 약 7nm)의 CeO2 그레인(grains)으로 구성되는 반면(도 6a 및 6b), 실리카(SiO2) 오버레이어에 의한 보호가 없는 경우 CeO2 결정체 및 Pd 금속 입자의 응집이 관찰된다(도 9 및 도 10). STEM(scanning transmission electron microscopy) 모드에서 EDS(Energy dispersive X-ray spectroscopy) 분석은 응집없이 Pd 종의 균질 분산을 보여준다(도 6c). 이러한 발견은 XRD(X-ray diffraction) 분석에 의해 뒷받침되며, CeO2를 제외한 회절 패턴은 관찰되지 않는다(도 7).6 to 10 , low-resolution and high-resolution transmission electron microscopy (HRTEM) images show that well-dispersed Pd/CeO 2 hollow nanoparticles are 10 nm or less (for example, about 7 nm) of CeO 2 grains. On the other hand ( FIGS. 6a and 6b ), in the absence of protection by the silica (SiO 2 ) overlayer, aggregation of CeO 2 crystals and Pd metal particles is observed ( FIGS. 9 and 10 ). Energy dispersive X-ray spectroscopy (EDS) analysis in scanning transmission electron microscopy (STEM) mode shows a homogeneous dispersion of Pd species without aggregation ( FIG. 6c ). This finding is supported by X-ray diffraction (XRD) analysis, and no diffraction patterns are observed except for CeO 2 ( FIG. 7 ).
EXAFS(extended X-ray absorption fine structure) 분석에서 Pd K 엣지 스펙트럼은 결정 형석 상에서 Pd-O와 Pd-Ce의 두 특성 거리의 존재를 보여준다(도 8). Pd-Pd 금속 결합에 해당하는 특징적인 피크는 관찰되지 않으며, 이는 XRD 데이터에 의해 입증된다. 이는 Pd 원자가 독점적으로 Ce 사이트에 위치한다는 것을 나타낸다. 사이트 특이적 구성은 Pd 원자 및 격자 산소의 직접적인 결합(Pd-O)에 상응하는 주 피크뿐만 아니라 분리된 Pd 주위의 국소 CeO2 환경(Pd-Ce)을 나타내는 작은 피크도 초래한다. EXAFS 곡선 피팅 분석을 통해 로컬 배위 환경을 조사할 수 있다. 최선의 피팅 곡선은 첫번째 피크가 첫 번째 Pd-O 쉘 배위에서 기원하는 반면 작은 두번째 피크는 Pd-Ce 두번째 쉘 배위에서 기원하는 것을 나타낸다(도 8).The Pd K edge spectrum in EXAFS (extended X-ray absorption fine structure) analysis shows the presence of two characteristic distances of Pd-O and Pd-Ce on crystalline fluorite (FIG. 8). No characteristic peak corresponding to the Pd-Pd metal bond is observed, which is evidenced by the XRD data. This indicates that the Pd atoms are located exclusively at the Ce site. The site-specific configuration results in a main peak corresponding to the direct bonding of Pd atoms and lattice oxygen (Pd-O), as well as a small peak representing the local CeO 2 environment (Pd-Ce) around the isolated Pd. EXAFS curve fitting analysis allows the investigation of the local coordination environment. The best-fitting curve shows that the first peak originates from the first Pd-O shell configuration while the small second peak originates from the Pd-Ce second shell configuration (Fig. 8).
표 1은 M/CeO2 중공 나노입자의 EXAFS 피팅을 요약해서 나타내고, 표 2는 ICP-AES에 의해 측정된 M/CeO2 중공 나노입자 내 원자의 농도를 나타낸다.Table 1 summarizes the EXAFS fitting of M/CeO 2 hollow nanoparticles, and Table 2 shows the concentration of atoms in M/CeO 2 hollow nanoparticles measured by ICP-AES.
[표 1][Table 1]
Figure PCTKR2021002574-appb-I000001
Figure PCTKR2021002574-appb-I000001
[표 2][Table 2]
Figure PCTKR2021002574-appb-I000002
Figure PCTKR2021002574-appb-I000002
도 11은 순수 CeO2 나노입자 및 다양한 M/CeO2 중공 나노입자의 XRD 패턴을 나타내고, 도 12는 다양한 M/CeO2 중공 나노입자의 TEM 이미지(low-magnification)를 나타내며((a) Pd, (b) Rh, (c) Ru), 도 13은 다양한 M/CeO2 중공 나노입자의 TEM 이미지(high-magnification)를 나타낸다((a) Pd, (b) Rh, (c) Ru). 도 14는 다양한 M/CeO2 중공 나노입자의 STEM-EDS 원소 맵핑(elemental mapping) 데이터를 나타내고((a) Pd, (b) Rh, (c) Ru), 도 15는 다양한 M/CeO2 중공 나노입자의 k3-weighted EXAFS 스펙트럼의 역푸리에 변환을 나타내며((a) Pd, (b) Rh, (c) Ru), 도 16은 다양한 M/CeO2 중공 나노입자의 k3-weighted EXAFS 스펙트럼의 푸리에 변환을 나타낸다((a) Pd, (b) Rh, (c) Ru).11 shows the XRD patterns of pure CeO 2 nanoparticles and various M/CeO 2 hollow nanoparticles, and FIG. 12 shows TEM images (low-magnification) of various M/CeO 2 hollow nanoparticles ((a) Pd, (b) Rh, (c) Ru), and FIG. 13 shows TEM images (high-magnification) of various M/CeO 2 hollow nanoparticles ((a) Pd, (b) Rh, (c) Ru). 14 shows STEM-EDS elemental mapping data of various M/CeO 2 hollow nanoparticles ((a) Pd, (b) Rh, (c) Ru), and FIG. 15 is various M/CeO 2 hollow nanoparticles. Inverse Fourier transform of the k 3 -weighted EXAFS spectrum of nanoparticles ((a) Pd, (b) Rh, (c) Ru), FIG. 16 is k 3 -weighted EXAFS spectrum of various M/CeO 2 hollow nanoparticles shows the Fourier transform of ((a) Pd, (b) Rh, (c) Ru).
도 11 내지 도 16을 참조하면, 이 변형된 랩-베이크-필 공정에 의해 Pd, Rh 및 Ru를 포함하여 다양한 원자로 분산된 금속이 CeO2 중공 나노입자의 Ce 공극에만 독점적으로 로딩되는 단일 원자 촉매가 형성될 수 있다.11 to 16 , by this modified lab-bake-fill process, metals dispersed into various atoms, including Pd, Rh, and Ru, are exclusively loaded into the Ce pores of CeO 2 hollow nanoparticles. Single atom catalyst can be formed.
페닐보론산(phenylboronic acid)과 에틸 4-브로모페닐아세테이트(ethyl 4-bromophenylacetate)의 연속 스즈키 커플링은 Pd/CeO2의 성능을 평가하기 위해 최적화된 조건 하에서 수행되었으며, 결과는 표 3에 제시되어 있다.The continuous Suzuki coupling of phenylboronic acid and ethyl 4-bromophenylacetate was performed under optimized conditions to evaluate the performance of Pd/CeO 2 , and the results are presented in Table 3 has been
[표 3][Table 3]
Figure PCTKR2021002574-appb-I000003
Figure PCTKR2021002574-appb-I000003
표 3을 참조하면, Pd/CeO2 중공 나노입자는 스즈키 커플링에 매우 효과적인 촉매인 것으로 나타났다. 특히 높은 선택도 (TOF > 160h-1, 선택도 > 97%)를 갖는다. PdIMP/CeO2 나노입자가 훨씬 낮은 선택도(약 80%)를 보여, Pd/CeO2 중공 나노입자의 높은 선택도는 그것의 독점적 활성 사이트에서 비롯된 것으로 보인다. 순수 CeO2 나노입자는 이 반응에서 불활성이었고, Pd/C(5wt.%)도 거의 불활성인 것으로 나타났다. 결과적으로, Pd/CeO2 중공 나노입자는 모든 조사된 불균일 촉매보다 우수한 성능을 보였으며 균일 Pd(OAc)2 촉매와 비슷한 성능을 보여주었다.Referring to Table 3, Pd/CeO 2 hollow nanoparticles were found to be very effective catalysts for Suzuki coupling. It has a particularly high selectivity (TOF > 160h −1 , selectivity >97%). Pd IMP /CeO 2 nanoparticles show much lower selectivity (about 80%), so the high selectivity of Pd/CeO 2 hollow nanoparticles appears to originate from their exclusively active sites. Pure CeO 2 nanoparticles were inactive in this reaction, and Pd/C (5 wt.%) was also almost inactive. As a result, Pd/CeO 2 hollow nanoparticles outperformed all investigated heterogeneous catalysts and showed similar performance to homogeneous Pd(OAc) 2 catalysts.
도 17은 스즈키 커플링에 대한 Pd/CeO2 중공 나노입자의 안정성 테스트 결과를 나타낸다.17 shows the stability test results of Pd/CeO 2 hollow nanoparticles for Suzuki coupling.
도 17을 참조하면, Pd/CeO2 중공 나노입자는 각 사이클 동안 TOF 및 선택도는 각각 약 160h-1 및 97%보다 큰 값에서 일정하게 유지되기 때문에 5 사이클 후에도 촉매 성능의 명백한 불활성화는 없었다. Referring to FIG. 17 , the Pd/CeO 2 hollow nanoparticles showed no apparent deactivation of the catalyst performance even after 5 cycles because the TOF and selectivity during each cycle remained constant at values greater than about 160 h −1 and 97%, respectively. .
도 18은 촉매 테스트 전후의 Pd/CeO2 중공 나노입자의 TEM 이미지를 나타낸다((a) 테스트 전, (b) 5회 테스트 후). 18 shows TEM images of Pd/CeO 2 hollow nanoparticles before and after the catalyst test ((a) before the test, (b) after 5 tests).
도 18을 참조하면, 5회 테스트 후 Pd/CeO2 중공 나노입자의 구조적 또는 화학적 저하의 징후는 검출되지 않았으며, 이는 Pd/CeO2 중공 나노입자가 우수한 안정성 및 재사용성을 갖는다는 것을 나타낸다.Referring to FIG. 18 , no signs of structural or chemical degradation of the Pd/CeO 2 hollow nanoparticles were detected after 5 tests, indicating that the Pd/CeO 2 hollow nanoparticles have excellent stability and reusability.
이제까지 본 발명에 대한 구체적인 실시예들을 살펴보았다. 본 발명이 속하는 기술 분야에서 통상의 지식을 가진 자는 본 발명이 본 발명의 본질적인 특성에서 벗어나지 않는 범위에서 변형된 형태로 구현될 수 있음을 이해할 수 있을 것이다. 그러므로 개시된 실시예들은 한정적인 관점이 아니라 설명적인 관점에서 고려되어야 한다. 본 발명의 범위는 전술한 설명이 아니라 특허청구범위에 나타나 있으며, 그와 동등한 범위 내에 있는 모든 차이점은 본 발명에 포함된 것으로 해석되어야 할 것이다.So far, specific embodiments of the present invention have been described. Those of ordinary skill in the art to which the present invention pertains will understand that the present invention can be implemented in a modified form without departing from the essential characteristics of the present invention. Therefore, the disclosed embodiments are to be considered in an illustrative rather than a restrictive sense. The scope of the present invention is indicated in the claims rather than the foregoing description, and all differences within an equivalent scope should be construed as being included in the present invention.
본 발명의 실시예들에 따른 단일 원자 촉매는 우수한 성능을 가질 수 있다.A single atom catalyst according to embodiments of the present invention may have excellent performance.

Claims (12)

  1. 세리아 중공 나노입자; 및ceria hollow nanoparticles; and
    상기 세리아 중공 나노입자에 로딩된 금속 원자를 포함하는 단일 원자 촉매.A single atom catalyst comprising a metal atom loaded onto the ceria hollow nanoparticles.
  2. 제 1 항에 있어서,The method of claim 1,
    상기 세리아 중공 나노입자는 10nm 이하의 세리아 그레인으로 구성되는 것을 특징으로 하는 단일 원자 촉매.The hollow ceria nanoparticles are single atom catalyst, characterized in that composed of ceria grains of 10 nm or less.
  3. 제 1 항에 있어서,The method of claim 1,
    상기 금속은 Pd, Rh, 및 Ru 중에서 적어도 하나를 포함하는 것을 특징으로 하는 단일 원자 촉매.The single atom catalyst, characterized in that the metal comprises at least one of Pd, Rh, and Ru.
  4. 제 1 항에 있어서,The method of claim 1,
    상기 단일 원자 촉매는 사이트 특이성을 갖는 것을 특징으로 하는 단일 원자 촉매.The single atom catalyst is a single atom catalyst, characterized in that it has site specificity.
  5. 제 1 항에 있어서,The method of claim 1,
    상기 금속 원자는 상기 세리아 중공 나노입자의 Ce 공극에 위치하는 것을 특징으로 하는 단일 원자 촉매.The metal atom is a single atom catalyst, characterized in that located in the Ce pore of the hollow ceria nanoparticles.
  6. 희생 코어를 형성하는 단계;forming a sacrificial core;
    상기 희생 코어 위에 세리아 층을 형성하는 단계;forming a ceria layer on the sacrificial core;
    상기 세리아 층에 금속 원자를 로딩하는 단계;loading metal atoms into the ceria layer;
    상기 세리아 층 위에 희생 코팅층을 형성하는 단계;forming a sacrificial coating layer on the ceria layer;
    상기 세리아 층을 열처리하는 단계; 및heat-treating the ceria layer; and
    상기 희생 코어 및 상기 희생 코팅층을 제거하는 단계를 포함하는 단일 원자 촉매의 형성 방법.and removing the sacrificial core and the sacrificial coating layer.
  7. 제 6 항에 있어서,7. The method of claim 6,
    상기 희생 코어 및 상기 희생 코팅층은 실리카로 형성되는 것을 특징으로 하는 단일 원자 촉매의 형성 방법.The method for forming a single atom catalyst, characterized in that the sacrificial core and the sacrificial coating layer are formed of silica.
  8. 제 6 항에 있어서,7. The method of claim 6,
    상기 열처리에 의해 상기 금속 원자는 상기 세리아 층에서 재분포되는 것을 특징으로 하는 단일 원자 촉매의 형성 방법.The method for forming a single atom catalyst, characterized in that by the heat treatment, the metal atoms are redistributed in the ceria layer.
  9. 제 6 항에 있어서,7. The method of claim 6,
    상기 열처리에 의해 상기 금속 원자는 상기 세리아 층의 Ce 공극에 배치되는 것을 특징으로 하는 단일 원자 촉매의 형성 방법. The method for forming a single atom catalyst, characterized in that by the heat treatment, the metal atoms are disposed in the Ce pores of the ceria layer.
  10. 제 6 항에 있어서,7. The method of claim 6,
    상기 희생 코팅층은 상기 열처리 동안 상기 세리아 층을 보호하는 것을 특징으로 하는 단일 원자 촉매의 형성 방법.wherein the sacrificial coating layer protects the ceria layer during the heat treatment.
  11. 제 6 항에 있어서,7. The method of claim 6,
    상기 희생 코어 및 상기 희생 코팅층이 제거되어 세리아 중공 나노입자가 형성되는 것을 특징으로 하는 단일 원자 촉매의 형성 방법.The method for forming a single atom catalyst, characterized in that the sacrificial core and the sacrificial coating layer are removed to form ceria hollow nanoparticles.
  12. 제 6 항에 있어서,7. The method of claim 6,
    상기 금속은 Pd, Rh, 및 Ru 중에서 적어도 하나를 포함하는 것을 특징으로 하는 단일 원자 촉매의 형성 방법.The method of forming a single atom catalyst, characterized in that the metal comprises at least one of Pd, Rh, and Ru.
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