Exploration of reaction pathway of cerium dioxide-based Pt catalyst for $CH_4$ oxidation = 이산화세륨 산화물 기반 백금 촉매의 메탄 산화에 대한 반응 경로 탐색에 관한 연구

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Identifying the key reaction site/pathway in oxide-supported metal nanoparticles is critical in designing high-performance catalysts for industrial chemical reactions, such as catalytic oxidation of methane. However, the high temperatures (> 673 K) required for $CH_4$ conversion cause the metal nanoparticles to aggregate into larger crystallite, which make it difficult to understand fundamental catalysis at a given condition. In this study, Pt nanoparticle catalysts are prepared via a colloidal synthesis to make the nanoparticles uniform, and then individual nanoparticles are encapsulated in porous oxide shells ($CeO_2$ or $SiO_2$) to allow chemical reaction through pores and to prevent agglomeration of nanoparticles at high temperatures. The key reaction sites are defined as a two-phase boundary (2PB) where gas and metal contact and a three-phase boundary (3PB) at which the gas, metal, and oxide support phases are in contact simultaneously. Each reaction site is then quantified through electron tomography and carbon monoxide oxidation/adsorption experiments as a 2PB area and 3PB length per gram of Pt. The density of each active site shows a different particle-size-dependency: 2PB density $\propto d^{-1}$, 3PB density $\propto d^{-2}$. By using these scaling relations, the dominant active site of the methane oxidation was investigated with respect to the Pt size, reaction temperature, and reactant concentration. Moreover, theoretical interpretation and ambient pressure X-ray photoelectron spectroscopy (AP-XPS) analysis provide a further understanding of the reaction mechanism and key surface-adsorbed species during methane oxidation. Based on the understanding of the active site and reaction pathway, the methane oxidation catalyst with improved activity was demonstrated. The results of this study provide a new approach on which to explore reaction pathways and mechanisms applicable to multiple reactions and materials.
Advisors
Jung, WooChulresearcher정우철researcher
Description
한국과학기술원 :신소재공학과,
Publisher
한국과학기술원
Issue Date
2020
Identifier
325007
Language
eng
Description

학위논문(박사) - 한국과학기술원 : 신소재공학과, 2020.8,[viii, 109 p. :]

Keywords

Pt nanoparticle▼a$CeO_2$▼acore-shell structure▼amethane oxidation reaction▼aactive site▼areaction pathway▼atwo-phase boundary(2PB)▼athree-phase boundary(3PB)▼aAP-XPS; 백금나노입자▼a이산화세륨▼a코어-쉘 구조▼a메탄 산화 반응▼a반응활성점▼a반응경로▼a2상경계면▼a3상경계면▼a엑스선 광전자 분광 기법

URI
http://hdl.handle.net/10203/284484
Link
http://library.kaist.ac.kr/search/detail/view.do?bibCtrlNo=926268&flag=dissertation
Appears in Collection
MS-Theses_Ph.D.(박사논문)
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