Quantitative analysis and surface characterization on supported Pt nanocatalysts for catalytic surface reaction = 촉매 표면화학 반응을 위한 백금 나노촉매의 정량분석 및 표면특성 분석 연구

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Understanding of heterogeneous catalysis has been one of the most important phenomena for resolving environmental energy problems using nanotechnologies such as synthesis of rational catalysts, reactor design, and the in situ techniques to characterize catalysts. CO oxidation reaction can be regarded as a prototypical reaction for probing the active sites and a benchmark system to investigate fundamental research and various applications. It is seemingly simple reaction but all factors of this reaction still remain a critical challenge to completely understand the process of surface reaction under real condition for applications. Various unprecedented surface chemistry studies have been conducted during chemical reactions that influence the catalytic activity and selectivity due to recent advances in surface analysis techniques including ambient XPS, STM, and IR spectroscopy. Therefore, to unravel fascinating molecular behaviors and develop practical catalysts with high performance, I have studied the realistic surface mechanism on Pt nanocatalysts under catalytic reaction with in situ surface-sensitive techniques. In this dissertation, Chapter 1 introduces the research background. In Chapter 2, I demonstrate the quantitative measurement of active sites on two-dimensional Pt arrays on the ultra-thin silicon wafers by measuring CO pulse chemisorption method. In addition, the effective active metal surface measured by CO chemisorption is quite lower than the apparent metal surface area derived from scanning electron microscopy or transmission electron microscopy images. Moreover, our experimental approach can provide meaningful information for extracting the true TOF of product molecules in gas-phase catalysis. In Chapter 3, I investigate the instantly formed surface oxide phase on the Pt nanoparticles under CO oxidation probed with an in situ IR spectroscopy. The abrupt blue shift of adsorbed CO probe on Pt surface is obviously related to the formation of ultrathin oxide layered Pt nanoparticles under catalytic reaction contributing to the enhanced catalytic reactivity. Therefore, the CO infrared spectroscopy, one of the surface-sensitive techniques, provide a strong evidence of vibrational frequency changes for detecting the surface oxide layer as an active species in catalysis. In Chapter 4, I demonstrate the significantly improved catalytic reactivity at the interface between Pt particles and crystalline mesoporous TiO2-x, which is promising catalytic support due to its outstanding thermal and chemical properties. Besides, unlike commercial titania, it has been confirmed that oxygen molecules can easily adsorb on the Pt/mesoporous TiO2-x interface. Furthermore, in situ vibrational motions of adsorbate molecules reveal the oxygen molecules at the Pt/mesoporous TiO2-x interface are activated by the diffusion of CO adsorbed on Pt surface, contributing to the improved reactivity. Thereby, a unique structure of crystalline porous titania with oxygen vacancies provides an effective and facile way to approach the study of CO oxidation mechanism in composite catalysts with titania-based supports.
Advisors
Park, Jeong Youngresearcher박정영researcher
Description
한국과학기술원 :화학과,
Publisher
한국과학기술원
Issue Date
2019
Identifier
325007
Language
eng
Description

학위논문(박사) - 한국과학기술원 : 화학과, 2019.8,[vi, 108 p. :]

Keywords

Pt nanocatalysts▼aactive sites▼asurface oxide layer▼ametal-oxide interface▼aactivated oxygen molecule▼ain situ IR spectroscopy▼aCO oxidation; 백금 나노촉매▼a활성사이트▼a표면산화층▼a금속-산화물 계면▼a산소분자 활성▼a실시간 적외선 분광법▼a일산화탄소 산화반응

URI
http://hdl.handle.net/10203/283392
Link
http://library.kaist.ac.kr/search/detail/view.do?bibCtrlNo=871567&flag=dissertation
Appears in Collection
CH-Theses_Ph.D.(박사논문)
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