서지주요정보
Light-assisted surface reactions using metal catalysts = 빛 에너지를 이용한 금속 촉매 표면 반응의 활성 향상
서명 / 저자 Light-assisted surface reactions using metal catalysts = 빛 에너지를 이용한 금속 촉매 표면 반응의 활성 향상 / Chanyeon Kim.
발행사항 [대전 : 한국과학기술원, 2018].
Online Access 원문보기 원문인쇄

소장정보

등록번호

8032386

소장위치/청구기호

학술문화관(문화관)B1층 보존서고

DCBE 18011

휴대폰 전송

도서상태

이용가능(대출불가)

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반납예정일

리뷰정보

초록정보

Metal nanoparticle have been intensively used as conventional catalysts in many chemical industries. Most of the catalytic processes supply energy required for the chemical reaction through heat transfer. The initiation of chemical reaction requires energy beyond activation energy, which is higher than the reaction enthalpy. Thus, excessive energy supply is inevitable. In addition, the selective energy transfer to the reactant among components of system including reactor, reaction medium, catalyst etc. is not possible in the energy transfer through thermal conduction and convection. In this regards, the conventional chemical process requires an excessive energy supply over the energy required for the reaction itself, which is leading to high reaction temperature. In this thesis, we design the new catalytic system to lower the reaction temperature by compensating the heat energy required for the chemical reaction with light energy. To this end, Plasmonic catalyst was designed as a new catalyst for effective absorption of light energy and light energy transfer mechanism was studied based on various experimental and theoretical evidence. Based on this understanding, a new type of light energy transfer mechanism that does not require the synthesis of complex catalyst structures through photoexcitation of metal-adsorbate.

금속 나노 입자 촉매는 기존의 여러 화학 산업에서 상용촉매로써 활발히 사용되어 왔다. 이때 대부분의 촉매 공정은 가열을 통해 반응에 필요한 에너지를 공급하게 된다. 화학 반응의 개시는 활성화 에너지의 극복을 요구하고 이는 반응 엔탈피 보다 높기 때문에 초과 에너지 공급이 불가피 하다. 또한 열 전도, 대류를 이용한 에너지 전달과정에서 반응물에 대한 선택적 에너지 전달이 불가능하므로 기존의 화학 공정은 반응 자체에 필요한 에너지 이상의 초과 공급을 요구하게 되며 이는 높은 반응 온도로 결부된다. 이에 본 학위논문에서는 화학반응에 요구되는 열 에너지를 빛 에너지로 보상함으로써 반응 온도를 낮추고자 한다. 이를 위해 금속 나노 입자를 이용해 빛 에너지를 효과적으로 흡수 및 전달할 수 있는 새로운 촉매 시스템이 고안 되었다. 효과적인 빛 에너지의 흡수를 위한 새로운 촉매로써 플라즈모닉 촉매를 설계하였으며 다양한 실험적, 이론적 증거들을 바탕으로 빛 에너지 전달 기제를 고찰하였다. 이 같은 이해를 바탕으로 복잡한 촉매 구조의 합성이 요구되지 않는 새로운 형태의 빛 에너지 전달 기제를 유도할 수 있었다.

서지기타정보

서지기타정보
청구기호 {DCBE 18011
형태사항 vi, 101 p. : 삽화 ; 30 cm
언어 영어
일반주기 저자명의 한글표기 : 김찬연
지도교수의 영문표기 : Hyunjoo Lee
지도교수의 한글표기 : 이현주
학위논문 학위논문(박사) - 한국과학기술원 : 생명화학공학과,
서지주기 References : p. 92-99
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Synthetic strategy ofAg-Ni binary nanoparticles

2 TEM images of (a) Ag-Ni snowman nanoparticles (Ag-Ni SM NPs) and (b) Ag@Ni core-shell nanoparticles (Ag@Ni CS NPs). Compositional analysis was conducted using HAADF images and elemental line scanning ofSTEM shown in (c)and (d) for Ag-Ni SM NPs; (e) and (f) for Ag@Ni CS NPs,respectively.

(a) Schematic illustration ofAg-Ni SM NP with an average size. The size distribution was obtained from counting 225nanoparticles. (b-d) Size distribution of overall, each Niand Ag part for the Ag-Ni SMNPs

(a) Schematic illustration ofAg@Ni CS NP with an average size. The size distribution was obtained from counting 304 nanoparticles. (b-d) Size distribution ofoverall, Ni shell and Ag core for the Ag@Ni CS NPs. The size ofthe Ni thin shell and Ag core was measured from HR-TEM images, thus only 20 nanoparticles were measured.

(a) HR-TEM image ofAg-Ni SM NP. FFT patterns for (b) the Agpart noted with a orange square in (a), and (c) the Ni part noted with a black square in (a). Each pattern exhibits <111> zone axis for (b) and <120> zone axis for(c). (d) HR-TEM image ofAg@NiCSNP

6 Powder XRD patterns for(a) Ag-Ni SM NPs and (b) Ag@Ni CS NPs with Rietveld refinements

7 TEM images of Ag-Ni SM NPs synthesized with (a) 1.8, (b) 1.4, (c) 1.0 and (d) 0.7 equivalents of TOP relative to the amount ofNi precursor used All of the nanoparticles were synthesized under the same conditions except for the amount ofTOP.

8 XPS data of as-made Ag-Ni binary nanoparticles: Ni 2p peaks for (a) Ag-Ni SM NPs and (b) Ag@Ni CS NPs; Ag4fpeak for (c) Ag-Ni SM NPs and (d) Ag@NiCS NPs. XPS data ofreduced Ag-Nibinary nanoparticles: Ni 2p peaks for (e) Ag-Ni SM NPs and (f) Ag@Ni CS NPs; Ag 4fpeak for (g) Ag-Ni SM NPs and (h) Ag@Ni CS NPs. All samples were reduced by bubbling H2 overnight while suspended in isopropyl alcohol.

9 Effect ofsurface reduction on the light absorption ofAg-Ni binary nanoparticles upon the treatments using (a, b)H2bubblingor (c,d) NaBH4.

10 (a) Absorption spectra and (b) Emission spectra for Ag-Ni snowman and Ag@Ni core-shell nanoparticles. All of the samples were dispersed in isopropyl alcohol and pre-reduced using NaBH4 solution prior to the measurement ofthe optical properties. In emission spectra, each sample was excited at its absorption maximum. (410nm for SM, 500nm for CS)

11 Spatial distribution ofthe surface plasmon induced enhancement ofelectromagnetic field intensity from FDTD calculations for (a)Ag-Ni SM NP and (b) Ag@Ni CS NP.

12 Time-dependent changes of the concentration of 4-nitrophenol, In(A/Ao) versus time, (a) without light and (b) with light. All data were normalized by the number of surface Ni atoms. (c) Enhancement factors, which represent the ratios between the rate constants without light (at 293 K) and with light, are displayed by orange columns. The experiment results without light at 303 K are also marked

TEM images with a low magnitude oftypical (a) Ag-Ni SM NPs (b) Ag@Ni CS NPs. Insets are HR images for each type ofnanoparticles

2 TEM images with a low magnitude oftypical (a) Ag NPs and (b) Ni NPs. Insets are HR images for each type ofnanoparticles

FT-IR spectra of pristine and annealed catalysts. (a) Ni/SiO2, (b) Ag-Ni SM/SiO2 and (c) Ag@Ni CS/SiO2.

Temperature programmed reduction analysis for annealed and reduced catalysts

CO chemisorption result for various catalysts

5 TEM images for pristine (a) Ag-Ni SM/SiO2, (b) Ag@Ni CS/SiO2 and surface treated (c) Ag-Ni SM/SiO2, (d) Ag@Ni CS/SiO2. The insets are HAADF images and elemental mapping for each sample. The white scale bars are 9 nm.

6 TEM images for (a) Ag-Ni SM NPs (b) Ag@Ni CS NPs before surface treatment, (c) Ag-Ni SM NPs and (d) Ag@Ni CS NPs after surface treatment, Nanoparticles were casted over Si/Au grid and treated under identical condition ofsupported nanoparticle catalysts

metallic states of various silica supported Ag-Ni and Ni nanoparticles before and after reduction using XPS analysis

7 Absorption spectra for silica supported Ag-Ni binary nanoparticle catalysts after surface treatment. Spectra were obtained using UV-Vis DRS.

8 Scheme ofreactor system for surface plasmon-assisted ethanol dehydrogenation

Ethanol dehydrogenation using supported nanoparticle catalysts

10 Yield of each product in the presence of various supported nanoparticles catalysts with or without light irradiation.

11 (a) Arrhenius plot ofvarious catalysts and b effective energy barrier (Eb) estimated from (a).

12 shape dependent characteristics ofAg-Nibinary nanoparticles, (a) Light intensity- (b) wavelength- dependent catalytic activity and (c, d) theoretical calculation based on FDTD method.

13 Energy profiles for dehydrogenation of ethanol and the formation of acetaldehyde on the neutral and charged Ni surface.

14 (a) Catalytic conversion with and without light. (b) Temperature programmed oxidation profiles for fresh and used catalysts.

Preparation conditions for various metal catalysts and crystalline sizes estimated from Scherrer equation based onPXRD.

1 CO2 conversion on CO2 hydrogenation for various transition metal catalysts with and without light irradiation. In typical experiments with light irradiation, 60mW/cm2 ofXe lamp was used. details about used catalysts are in Table 4.1

2Light intensity and wavelength dependent measurement of photocatalytic CO2 hydrogenation using (a,b) Ru/SiO2 and (c,d) Rh/SiO2 In (b,d), AX/AZ was calculated by gradient of CO2 conversion divided by gradient of wavelength oflong pass filters.

3 Effect of surface Ru oxide on CO2 hydrogenation using samples with different annealing times at 500'C in the air, 0 min for 89% metallic Ru, 1 min for 56% metallic Ru and 60 min for 39% metallic Ru. metallic state ofRu for each sample was estimated by XPS.

CO2 conversion on CO2 hydrogenation for Ru/SiO2 with different Ru sizes

Characterization results of Ru/SiO2 with different Ru sizes. Metallic Ru for each catalyst was controlled to similar level using reduction treatment with 200 ccm of10% H2/N2at300 'C for3 hr.

5 Calculated (a) CO2 binding energy and (b) HOMO-LUMO gap ofadsorbed CO2 on Ru surface and that offree CO2 using DFT.

6 Modeled metal surface structure and calculated atomic sites. (a)Top view ofthe calculated surface (111) for fcc structure (Cu, Pt, Ni, Rh). The labeled sites are (1) fcc hollow, (2) hcphollow, (3) bridge, and (4) on top site. (b) Top view of the surface (0001) for hcp structure (Ru). The labeled sites are (1)hcphollow, (2) fcc hollow, and (3) on top site. The initial configurations ofCO2 molecul

7 (a) DRIFT spectra during CO2 adsorption using Ru/SiO2. Spectra were obtained in order to following steps, CO2 adsorption using 50 ccm of0.5% CO2/N2 for 10min. After that, 50 ccm ofN2 purging for 15min to desorb the weakly adsorbed CO2. (b) DRIFT spectra during hydrogenation ofabsorbed CO2 over Ru catalyst. Spectra were obtained in order to following steps, CO2 adsorption using 50 ccm of0.5% CO2/

8 effect oflight on CO hydrogenation using Ru catalyst

9 DRIFT spectra during (a) CO adsorption and (b) hydrogenation of absorbed CO over Ru catalyst Spectra were obtained in order to following steps, CO adsorption using 50 ccm of 1% CO/N2 for 10min. After that, 50 ccm ofN2 purging for 15min to desorb the weakly adsorbed CO In case of(a), spectra were measured after N2 purging. then spectra in (b) were measured after 10 min ofdiluted hydrogen flowing,

10 Scheme oflight-assisted CO2 hydrogenation through strong CO2 adsorption

11 Power consumption during thermal and light system for CO2 hydrogenation. Measurement conditions for thermal system was identical to catalytic performance test under dark condition excepting temperature, at 180 'C. In case oflight system, 532nm 100mW laser equipped with beam expander was used as light source and temperature ofsystem was 150 'C. Final energy assessment was conducted using accumul

12 Response test for thermally driven and light enhanced CO2 hydrogenation. In measurement of thermally driven system, furnace was turned on at the beginning and kepton for 3hr after system reached at 250 C. For light enhanced system, system was preheated to 100 C then catalytic performance was monitored with 100mW/cm2 of light intensity using Xe lamp alternating light irradiation condition, turni

13 Light-assisted hydrogenation with 10% CO2 feed using 5.6nm Ru catalysts with 10mg Ru basis. In typical experiments with light irradiation, 100mW/cm2 ofXelamp was used.