東華大學圖書館 |

語系: 繁體中文

說明(常見問題)

回圖書館首頁

手機版館藏查詢

登入

回首頁

切換: 標籤 | MARC模式 | ISBD

Surface Effects in State-Resolved Ga...

High, Eric A.

FindBook

Google Book

Amazon

博客來

Surface Effects in State-Resolved Gas-Surface Reactions.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Surface Effects in State-Resolved Gas-Surface Reactions./
作者:	High, Eric A.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2020,
面頁冊數:	193 p.
附註:	Source: Dissertations Abstracts International, Volume: 81-09, Section: B.
Contained By:	Dissertations Abstracts International81-09B.
標題:	Chemistry. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=27735765
ISBN:	9781658416764

Surface Effects in State-Resolved Gas-Surface Reactions.
High, Eric A.

Surface Effects in State-Resolved Gas-Surface Reactions. - Ann Arbor : ProQuest Dissertations & Theses, 2020 - 193 p.

Source: Dissertations Abstracts International, Volume: 81-09, Section: B.

Thesis (Ph.D.)--Tufts University, 2020.

This item must not be sold to any third party vendors.

The dissociative chemisorption of methane on transition metal surfaces has proven a productive model system for the observance of mode-specific and bond-selective reactions trends. More recently, the narrow energetic distributions afforded by narrow-bandwidth IR laser excitation of a supersonically expanded molecular beam has also proven useful for testing surface specific effects. With researchers in the field beginning to move toward the study of more complex systems, there is a desire to generalize the nonstatistical and/or surface specific trends observed for methane. However, there are still significant gaps in our understanding of the mechanism of surface induced energy flow within the approaching gas molecule. The observed trends have also been limited to a relatively limited number of low-index surfaces and surface temperatures well-below those used in industry.In this work, we studied the reactivity of methane on flat and stepped nickel surfaces across a wide range of incident energies and surface temperatures. We employed C-H stretch selective excitation of CH2D2 and found identical reactivity of the symmetric and antisymmetric modes on Ni(111). This result contrasts with previously reported vibrational state ordering for CH4 suggesting that the degeneracy of the stretching states may play a role. Theoretical work based on the reaction path Hamiltonian (RPH) by our collaborators verifies that different coupling strengths between the stretching oscillators have a large impact on the reaction probability of the excited molecules. Bond-selective measurements confirm that this energy exchange is limited to similar oscillators within the C-H manifold. The nozzle temperature dependence of bond-selective cleavage in selectively excited molecules is also discussed for the first time.A slight modification to well-employed beam reflectivity methods allowed for the study of carbon dissolution on the stepped nickel surface with a molecular beam of CH4 on a moderately stepped Ni(997) surface. These results indicate a rapid shift in rate of carbon uptake through the (997) plane at a surface temperature of 700 K. The application of a proven model based on the surface local equilibrium hypothesis predicts a bulk diffusion barrier in line with those reported on low-index Ni surfaces and highlights the significance of the step edges. Dissolution measurements were also used to investigate coverage dependent reactivity.Finally, CH4 and CD4 dissociation were studied at surface temperatures approaching those used in industrial reactors on the stepped Ni surface. These measurements mark the first state-resolved study of methane dissociation on a high-index plane of nickel. In contrast to Ni(111), methane dissociation on the Ni(997) displayed a complete lack of surface temperature dependence from 500 to 1000 K. Additionally, the reactivity on the stepped surface was lower than measurements on the (111) plane at high incident energies suggesting a greater density of reaction sites on the atomically flat single crystal. Angle-resolved measurements confirm significant reactivity contributions from the terrace atoms under the conditions in this study.

ISBN: 9781658416764Subjects--Topical Terms:

516420
Chemistry.
Subjects--Index Terms:

Carbon dissolution

Surface Effects in State-Resolved Gas-Surface Reactions.
LDR:04342nmm a2200373 4500 001 2266102
005 20200608114759.5
008 220629s2020 ||||||||||||||||| ||eng d
020 $a 9781658416764
035 $a (MiAaPQ)AAI27735765
035 $a AAI27735765
040 $a MiAaPQ $c MiAaPQ
100 1 $a High, Eric A. $3 3543288
245 1 0 $a Surface Effects in State-Resolved Gas-Surface Reactions.
260 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 2020
300 $a 193 p.
500 $a Source: Dissertations Abstracts International, Volume: 81-09, Section: B.
500 $a Advisor: Utz, Arthur L.
502 $a Thesis (Ph.D.)--Tufts University, 2020.
506 $a This item must not be sold to any third party vendors.
520 $a The dissociative chemisorption of methane on transition metal surfaces has proven a productive model system for the observance of mode-specific and bond-selective reactions trends. More recently, the narrow energetic distributions afforded by narrow-bandwidth IR laser excitation of a supersonically expanded molecular beam has also proven useful for testing surface specific effects. With researchers in the field beginning to move toward the study of more complex systems, there is a desire to generalize the nonstatistical and/or surface specific trends observed for methane. However, there are still significant gaps in our understanding of the mechanism of surface induced energy flow within the approaching gas molecule. The observed trends have also been limited to a relatively limited number of low-index surfaces and surface temperatures well-below those used in industry.In this work, we studied the reactivity of methane on flat and stepped nickel surfaces across a wide range of incident energies and surface temperatures. We employed C-H stretch selective excitation of CH2D2 and found identical reactivity of the symmetric and antisymmetric modes on Ni(111). This result contrasts with previously reported vibrational state ordering for CH4 suggesting that the degeneracy of the stretching states may play a role. Theoretical work based on the reaction path Hamiltonian (RPH) by our collaborators verifies that different coupling strengths between the stretching oscillators have a large impact on the reaction probability of the excited molecules. Bond-selective measurements confirm that this energy exchange is limited to similar oscillators within the C-H manifold. The nozzle temperature dependence of bond-selective cleavage in selectively excited molecules is also discussed for the first time.A slight modification to well-employed beam reflectivity methods allowed for the study of carbon dissolution on the stepped nickel surface with a molecular beam of CH4 on a moderately stepped Ni(997) surface. These results indicate a rapid shift in rate of carbon uptake through the (997) plane at a surface temperature of 700 K. The application of a proven model based on the surface local equilibrium hypothesis predicts a bulk diffusion barrier in line with those reported on low-index Ni surfaces and highlights the significance of the step edges. Dissolution measurements were also used to investigate coverage dependent reactivity.Finally, CH4 and CD4 dissociation were studied at surface temperatures approaching those used in industrial reactors on the stepped Ni surface. These measurements mark the first state-resolved study of methane dissociation on a high-index plane of nickel. In contrast to Ni(111), methane dissociation on the Ni(997) displayed a complete lack of surface temperature dependence from 500 to 1000 K. Additionally, the reactivity on the stepped surface was lower than measurements on the (111) plane at high incident energies suggesting a greater density of reaction sites on the atomically flat single crystal. Angle-resolved measurements confirm significant reactivity contributions from the terrace atoms under the conditions in this study.
590 $a School code: 0234.
650 4 $a Chemistry. $3 516420
650 4 $a Physical chemistry. $3 1981412
653 $a Carbon dissolution
653 $a Methane activation
653 $a Molecular beam
653 $a State resolved
653 $a Surface structure
653 $a Surface temperature
690 $a 0485
690 $a 0494
710 2 $a Tufts University. $b Chemistry. $3 1058685
773 0 $t Dissertations Abstracts International $g 81-09B.
790 $a 0234
791 $a Ph.D.
792 $a 2020
793 $a English
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=27735765