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Synthesis of template-induced hollow nanostructures and study on their heterogeneous catalytic properties = 주형을 통한 중공 나노 구조체의 합성과 불균일계 촉매적 특성에 관한 연구
서명 / 저자 Synthesis of template-induced hollow nanostructures and study on their heterogeneous catalytic properties = 주형을 통한 중공 나노 구조체의 합성과 불균일계 촉매적 특성에 관한 연구 / Bu-Seo Choi.
발행사항 [대전 : 한국과학기술원, 2016].
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Research for the metal nanoparticles and nanostructures is under active discussion and development in the field of nanoscience and nanotechnology due to their promising applicable potentials. The properties of the metal nanostructures are sensitive to their size, composition, morphology (described by the shape, dimensional anisotropy, structure, and crystallinity). Most of all, thanks to their unique property, hollow nanostructures with porous framework have advantages of enhancing the catalytic activity and stability or optimizing the catalytic efficiency. In chapter 2, the study on the multi-metallic alloy nanotubes with nanoporous framework was de-scribed. co-reduction of multiple metal precursors with sodium citrate in the presence of ZnO nanowires rapidly yielded Pt-Pd, Pt-Ag, and Pd-Ag binary alloy nanotubes, as well as Pt-Pd-Ag ternary alloy nanotubes. The pre-pared multi-metallic nanotubes possess nanoporous frameworks composed of three-dimensionally intercon-nected nanoparticles, resulting in improved catalytic activities and stabilities toward alcohol electro-oxidation as well as mechanical robustness. In chapter 3, the study on one-pot self-templating synthesis of Pt hollow nanostructures and their cata-lytic properties for CO oxidation was described. well-defined Pt hollow nanostructures with octahedral and hexagonal frame-like morphologies were prepared by a facile one-pot self-templating route with no assistance of preformed template or shape-directing agent. The hexagonal frame-like Pt hollow structures exhibited signif-icantly enhanced catalytic activity toward CO oxidation reaction compared to the octahedral Pt hollow nanostructures due to their higher oxidation state of Pt.

금속 나노 입자는 다양한 분야에서 응용될 수 있어 활발히 연구되고 있는 물질이다. 나노 입자의 제조 방법들 중 bottom-up 방식은 나노 입자의 균일성을 높이고 성분 및 크기 조절 등이 용이하여 많이 이용되는 방법이며, 나노 입자의 크기를 조절하여 표면적을 넓히는 것을 넘어서 모양이 조절된 나노 입자도 합성할 수 있게 한다. 그 중에서도 다공성 정공 구조로 조절된 나노 입자는 구조가 주는 특이성으로 인해 반응의 효율이나 선택성을 높일 수 있는 이점이 있고, 이로 인해 촉매적 효율을 최적화 시킬 수 있기 때문에 연구의 가치가 높다. 2장에서는 나노 다공성 틀 구조의 다중 금속 나노 튜브에 관한 연구를 다룬다. 기판 위에 자란 산화아연 나노 와이어를 템플레이트로 이용하여 여러 종류의 금속 전구체들이 그 표면 위에서 환원되도록 유도하는 방법을 연구하였고, Pt-Pd, Pt-Ag, 또는 Pd-Ag로 구성된 이중 금속 나노 튜브와 Pt-Pd-Ag로 이루어진 삼중 금속 나노 튜브를 합성할 수 있었다. 합성된 다중 금속 나노 튜브는 연료 전지의 음극에서 일어나는 반응 중 하나인 에탄올 산화 반응에 대하여 높은 촉매 활성 및 안정성을 보였고, 플렉서블 기판 위에 구현된 패턴화된 금속 나노 튜브 어셈블리도 높은 기계적 강도를 나타내었다. 3장에서는 속이 빈 모양의 Pt 나노촉매의 합성과 이들의 일산화탄소 산화 반응에 대한 촉매 활성도에 관한 연구를 다룬다. One-Pot 자가주형 방법으로 Pt 전구체와 Ag 전구체로 이루어진 코디네이션 폴리머를 합성하고 이를 통해 정8면체 정공모양과 육각링 모양을 가지는 Pt 나노구조 제조기술을 개발하였다. 합성된 나노구조체는 XPS 표면 분석을 통해 각각 Pt와 Pt oxide 상태로 존재함을 확인할 수 있었고, 일산화탄소 산화반응에 대하여 백금의 산화상태가 높은 육각링 모양의 나노구조체가 산화상태가 낮은 정8면체 정공모양의 나노구조체보다 활성이 높게 나타나는 것을 확인하였다.

서지기타정보

서지기타정보
청구기호 {DCH 16008
형태사항 69 p. : 삽화 ; 30 cm
언어 영어
일반주기 저자명의 한글표기 : 최부서
지도교수의 영문표기 : Sang Woo Han
지도교수의 한글표기 : 한상우
수록잡지명 : "Multi-Metallic Alloy Nanotubes with Nanoporous Framework". ACS Nano, v.6.no.6, pp.5659-5667(2012)
수록잡지명 : "One-Pot Self-Templating Synthesis of Pt Hollow Nanostructures and Their Catalytic Properties for CO Oxidation". Chemistry-A European Journal, v.20.no.26, pp.11669-11674(2014)
학위논문 학위논문(박사) - 한국과학기술원 : 화학과,
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(a) SEM and (b) TEM images of the pristine ZnO NWs grown on Si wafer by hydrothermal syn-

(a) SEM, (b) TEM, and (c) HAADF-STEM-EDS mapping images ofthe Pt-Pd NTs. HRTEM im- age is shown in the inset of(b). (d) SEM, (e) TEM, and (f) HAADF-STEM-EDS mapping images ofthe Pt-Ag NTs. HRTEM image is shown in the inset of (e). (g) SEM, (h) TEM, and (i) HAADF-STEM-EDS mapping images of the Pd-AgNTs. HRTEM image is shown in the inset of(h). The scale bars in insets of(b), (e), and (h) indicate 2

High-magnification TEM images of (a) Pt-Pd, (b) Pt-Ag, (c) Pd-Ag, and (d) Pt-Pd-Ag NT

HAADF-STEM images and cross-sectional compositional line profiles of (a) Pt-Pd, (b) Pt-Ag,(C] Pd-Aa. and (d) pt-Pd-AaNTs. Thescale barsindicate 50 nm.

(a) SEM, (b) TEM, and (c) HAADF-STEM-EDS mappingimages of the Pt-Pd-AgNTs. HRTEN imageis shown in theinset.of (b). Thescale barin (c)indicates 50 nm.

XRD patterns of the pristine ZnO NWs, Pt-Pd, Pt-Ag, Pd-Ag, and Pt-Pd-Ag NTs. The positions and intensities for pure Pt, Pd, and Ag references were taken from the JCPDS database (Pt: 04-0802, Pd: 65- 6174, Ag:04-0783). Observed three peaks for each NT can be indexed to the (111), (200), and (220) reflec- tions of face-centered cubic (fcc) structure of metal, showing the pure crystalline nature of t

TEM images of Pt-Pd-Ag/Zn0 nanostructures collected at different reaction times: (a)0, (b) 10, (c) 20, (d) 30, and (e) 40 min. HRTEM images are shown in the insets of (a) and (b). The scale bars in the in- sets of (a) and (b) indicate 2 nm. The red circles in the inset of(b) denote the small nanoparticles grown on the surface ofZnO NW. (f) Changes in the molar ratios ofZn, Pt, Pd, and Ag during th

HAADF-STEM-EDS mapping imagesofthe Pt-Pd-Ag NTs obtained after1 hofreaction time

(a) SEM image Ag nanostructures prepared by the reduction ofAg+ with citrate in the absence of ZnO NWs. SEM images of nanostructures prepared by the reduction of (b) PtCl425, (c) PdCl42, and (d) Ag+

SEM images of (a) Pt-Pd, (b) Pt-Ag, (c) Pd-Ag, and (d) Pt-Pd-Ag nanostructures prepared

The ICP-AES-determined compositions of multi-metallic NTs prepared by controlling the relative amounts of metal precursors in growth solution.

SEM images of the Pt-Pd NTson ITO (a) before and (b) afterthe durability test. TEM images of the Pd/C (C) before and (d) afterthedurabilitytest.

(a) TEM image ofthe dendritic Pt-Pd NPs. HAADF-STEM image and cross-sectional composi- tional line profiles ofPt-Pd NPsshown in inset clearly demonstrate thatthe prepared NPs are Pt-Pd alloys. The

(a) CVs in 0.1 M KOH+ 0.5 M ethanol ofthe Pt-Pd NTs,Pt-PdNPs, PdNTs, and Pd/C on ITO electrodes. Scan rate: 50 mVs-1.(b) CA curves for the Pt-Pd NTs, Pt-Pd NPs,Pd NTs, and Pd/C at -0.1 V VS. Ag/AgCl. CVs in 0.1 M KOH + 0.5 M ethanol ofthe Pt-Pd NTs (c) and Pd/C (d) before and after durability test. (e) Normalized current densities of the Pt-Pd NTs and Pd/C toward ethanol electro-0xidation as a fun

CVs in 0.1 M KOH for the Pt-Pd NTs, Pt-Pd NPs, Pd NTs, and Pd/C on ITO electrodes. Scan rate: 50 mVs1. The current values were normalized with respect to the electrochemically active surface areas (ECSA), which were calculated by measuring the coulombic charges for oxygen desorption to avoid the inter- ference ofhydrogen absorption in Pd. The ECSA was estimated by the following equation; ECSA : Qo

XPS spectra for the Pd 3d core levels of the Pt-Pd and Pd NTs.

TEM images ofthe Pt-PdNTs (a) before and (b) afterthe 30 Sec ofCA measurement.

(a) SEM image ofletter pattern ofPt-Pd-AgNTs. (b) High-magnification SEM images ofPt-Pd- Ag NTs. (c) SEM-EDS elemental mapping images ofPt-Pd-Ag NT pattern shown in (a). (d) SEM images of pristine dot pattern ofPt-Pd-Ag NTs on PI substrate. SEM images ofthe dot pattern ofPt-Pd-Ag NTs after 105 cycles of(e) positive and (f) negative bending and relaxing with a radius of curvature of4.00 mm. The sca

Photographs of the reaction solutions before and after the reaction of (a) K2PtCl4 and (b) K2PtCl precursors with citrate in the absence ofAg+ ions. TEM image of the productprepared with the K2PtC14 pre cursoris shown in the insetof (a). The scale barindicates 2 nm.

(a) SEM, (c) TEM, and (e) HRTEM images of the OHNPs. (b) SEM, (d) TEM, and (f) HRTEM images ofthe HNFs. XPSspectra forthe Pt4fcore levels ofthe (g) OHNPs and (h) HNFs.

HAADF-STEM images and cross-sectional compositional line profiles of the (a) OHNPs and (b) HNFs.Thescale bars indicate 30 nm (a) and 200 nm (b).

SEM images of the as-prepared (a,b) OHNPs and (c,d) HNFS (a,c) before and (b,d) afterthe treat mentwith acmep0110 ammenia colutian

XRD patterns of the OHNPs and HNFs. The positions and intensities for pure Pt, PtO, and a-PtO were taken from theJCPDS database.

SEM images ofthe (a) octahedral and (b) hexagonal plate-like coordination polymers. (c)A poly- meric network of the octahedral coordination polymer viewed along the different axes. Pt, Ag, and Cl atoms are presented as blue, pink, and gray colors, respectively. Due to its high-level crystallographic symmetry in the unit cell (space group; I41/A), each atom reproduced 16 times in the unitcell by it

HAADF-STEM-EDS elemental mappingimagesof the octahedral coordination polymers.

SEM images of the (a) octahedral and (c) hexagonal plate-like coordination polymers prepare with the differentrelative amountofAg+ions and corresponding (b) OHNPs and (d) HNFS. The scale barsil (a) and (b) indicate 300 nm, and thosein (c) and (d) indicate 1 um.

(a) The Rietveld plot of the octahedral co- ordination polymer. Red crosses indicate the observed points in the XRD experiment. The green solid line is the fitted line. The black marks and the magenta line mean the allowed reflection positions and the difference line, respectively. The plot is scaled 4 times after 60d to show more clearly at the high angle region. The back-

XPS spectra for the (a)Pt4f, (b) Cl2p, and (c) Ag 3d core levels ofthe octahedral (red) and hex- agonal plate-like (blue) coordination polymers, and commercial AgCl (black). Table shown below the XPS spectra summarizes the peak positions for the Pt4f712, Cl2p3/2, and Ag 3ds.2 core levels of different samples.

Changes in the UV-Vis extinction spectra of(a) K2PtCl4 and (b) K2PtCl6 aqueous solutions during

Changesin the UV-Vis extinction spectra ofthe reaction solutions during the reaction prc the (a) OHNPs and (b) HNFs. (c) TEM images of nanostructures, which were prepared with PtCl42- pre collected at different reaction times: (c1) 0 (before heating), (c2) 5, (c3) 30, and (c4) 90 min. The SC: indicate 10 nm. (d) Proposed self-templating mechanism forthe formation ofthe Pthollow nanostructu

SEM images of the (a,b) octahedral and (c,d) hexagonal plate-like coordination polymers (a,C, before and (b,d) after the heat treatment at ~100 우C for1h.

Catalytic activity of the OHNPs and HNFs for the C0 oxidation reaction: (a) TOFs at different temperatures and (b) Arrhenius plots.