Author: Keith Benton Rider
Publisher:
ISBN:
Category :
Languages : en
Pages : 310
Book Description
High Pressure, High Temperature Scanning Tunneling Microscopy Studies of CO, NO, and 02 on Pt(111) and Rh(111)
High Pressure Scanning Tunneling Microscopy Studies of Adsorbate Structure and Mobility During Catalytic Reactions
Scanning Tunneling Microscopy Studies of the Structures and Dynamics of Molecular Monolayers on the Rh(111) and Pt(111) Single Crystal Surfaces
Dissertation Abstracts International
Author:
Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 860
Book Description
Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 860
Book Description
Adsorbate Structures and Catalytic Reactions Studied in the Torr Pressure Range by Scanning Tunneling Microscopy
Author: Kevin Shao-Lin Hwang
Publisher:
ISBN:
Category :
Languages : en
Pages : 272
Book Description
Publisher:
ISBN:
Category :
Languages : en
Pages : 272
Book Description
High Pressure Scanning Tunneling Microscopy Studies of AdsorbateStructure and Mobility During Catalytic Reactions
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 277
Book Description
The aim of the work presented therein is to take advantage of scanning tunneling microscope’s (STM) capability for operation under a variety of environments under real time and at atomic resolution to monitor adsorbate structures and mobility under high pressures, as well as to design a new generation of STM systems that allow imaging in situ at both higher pressures (35 atm) and temperatures (350 °C).
Publisher:
ISBN:
Category :
Languages : en
Pages : 277
Book Description
The aim of the work presented therein is to take advantage of scanning tunneling microscope’s (STM) capability for operation under a variety of environments under real time and at atomic resolution to monitor adsorbate structures and mobility under high pressures, as well as to design a new generation of STM systems that allow imaging in situ at both higher pressures (35 atm) and temperatures (350 °C).
Adsorbate Structures and Catalytic Reactions Studied in the Torrpressure Range by Scanning Tunneling Microscopy
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 132
Book Description
High-pressure, high-temperature scanning tunneling microscopy (HPHTSTM) was used to study adsorbate structures and reactions on single crystal model catalytic systems. Studies of the automobile catalytic converter reaction [CO + NO → 1/2 N2 + CO2] on Rh(111) and ethylene hydrogenation [C2H4 + H2 → C2H6] on Rh(111) and Pt(111) elucidated information on adsorbate structures in equilibrium with high-pressure gas and the relationship of atomic and molecular mobility to chemistry. STM studies of NO on Rh(111) showed that adsorbed NO forms two high-pressure structures, with the phase transformation from the (2 x 2) structure to the (3 x 3) structure occurring at 0.03 Torr. The (3 x 3) structure only exists when the surface is in equilibrium with the gas phase. The heat of adsorption of this new structure was determined by measuring the pressures and temperatures at which both (2 x 2) and (3 x 3) structures coexisted. The energy barrier between the two structures was calculated by observing the time necessary for the phase transformation to take place. High-pressure STM studies of the coadsorption of CO and NO on Rh(111) showed that CO and NO form a mixed (2 x 2) structure at low NO partial pressures. By comparing surface and gas compositions, the adsorption energy difference between topsite CO and NO was calculated. Occasionally there is exchange between top-site CO and NO, for which we have described a mechanism for. At high NO partial pressures, NO segregates into islands, where the phase transformation to the (3 x 3) structure occurs. The reaction of CO and NO on Rh(111) was monitored by mass spectrometry (MS) and HPHTSTM. From MS studies the apparent activation energy of the catalytic converter reaction was calculated and compared to theory. STM showed that under high-temperature reaction conditions, surface metal atoms become mobile. Ethylene hydrogenation and its poisoning by CO was also studied by STM on Rh(111) and Pt(111). Poisoning was found to coincide with decreased adsorbate mobility. Under ethylene hydrogenation conditions, no order is detected by STM at 300 K, as hydrogen and ethylidyne, the surface species formed by gas-phase ethylene, are too mobile. When CO is introduced, the reaction stops, and ordered structures appear on the surface. For Rh(111), the structure is predominantly a mixed c(4 x 2), though there are some areas of (2 x 2). For Pt(111), the structure is hexagonal and resembles the Moire pattern seen when Pt(111) is exposed to pure CO. From these studies it is concluded that CO poisons by stopping adsorbate mobility. This lack of adsorbate mobility prevents the adsorption of ethylene from the gas phase by hindering the creation of adsorption sites.
Publisher:
ISBN:
Category :
Languages : en
Pages : 132
Book Description
High-pressure, high-temperature scanning tunneling microscopy (HPHTSTM) was used to study adsorbate structures and reactions on single crystal model catalytic systems. Studies of the automobile catalytic converter reaction [CO + NO → 1/2 N2 + CO2] on Rh(111) and ethylene hydrogenation [C2H4 + H2 → C2H6] on Rh(111) and Pt(111) elucidated information on adsorbate structures in equilibrium with high-pressure gas and the relationship of atomic and molecular mobility to chemistry. STM studies of NO on Rh(111) showed that adsorbed NO forms two high-pressure structures, with the phase transformation from the (2 x 2) structure to the (3 x 3) structure occurring at 0.03 Torr. The (3 x 3) structure only exists when the surface is in equilibrium with the gas phase. The heat of adsorption of this new structure was determined by measuring the pressures and temperatures at which both (2 x 2) and (3 x 3) structures coexisted. The energy barrier between the two structures was calculated by observing the time necessary for the phase transformation to take place. High-pressure STM studies of the coadsorption of CO and NO on Rh(111) showed that CO and NO form a mixed (2 x 2) structure at low NO partial pressures. By comparing surface and gas compositions, the adsorption energy difference between topsite CO and NO was calculated. Occasionally there is exchange between top-site CO and NO, for which we have described a mechanism for. At high NO partial pressures, NO segregates into islands, where the phase transformation to the (3 x 3) structure occurs. The reaction of CO and NO on Rh(111) was monitored by mass spectrometry (MS) and HPHTSTM. From MS studies the apparent activation energy of the catalytic converter reaction was calculated and compared to theory. STM showed that under high-temperature reaction conditions, surface metal atoms become mobile. Ethylene hydrogenation and its poisoning by CO was also studied by STM on Rh(111) and Pt(111). Poisoning was found to coincide with decreased adsorbate mobility. Under ethylene hydrogenation conditions, no order is detected by STM at 300 K, as hydrogen and ethylidyne, the surface species formed by gas-phase ethylene, are too mobile. When CO is introduced, the reaction stops, and ordered structures appear on the surface. For Rh(111), the structure is predominantly a mixed c(4 x 2), though there are some areas of (2 x 2). For Pt(111), the structure is hexagonal and resembles the Moire pattern seen when Pt(111) is exposed to pure CO. From these studies it is concluded that CO poisons by stopping adsorbate mobility. This lack of adsorbate mobility prevents the adsorption of ethylene from the gas phase by hindering the creation of adsorption sites.
Current Trends of Surface Science and Catalysis
Author: Jeong Young Park
Publisher: Springer Science & Business Media
ISBN: 1461487420
Category : Science
Languages : en
Pages : 265
Book Description
This unique book covers the latest surface science studies on model catalysts, including single crystals, non-colloidal nanocatalysts, and nanoparticles in various forms with the control of size, shape and composition. This book addresses the issue of bridging “materials and pressure gaps” and also discusses the important issue of metal-oxide interface and hot electron flows in heterogeneous catalysis. The current development of in-situ surface techniques that is relevant to bridging “pressure gaps” is also highlighted.
Publisher: Springer Science & Business Media
ISBN: 1461487420
Category : Science
Languages : en
Pages : 265
Book Description
This unique book covers the latest surface science studies on model catalysts, including single crystals, non-colloidal nanocatalysts, and nanoparticles in various forms with the control of size, shape and composition. This book addresses the issue of bridging “materials and pressure gaps” and also discusses the important issue of metal-oxide interface and hot electron flows in heterogeneous catalysis. The current development of in-situ surface techniques that is relevant to bridging “pressure gaps” is also highlighted.
Scanning Tunneling Microscopy I
Author: Hans-Joachim Güntherodt
Publisher: Springer Science & Business Media
ISBN: 3642973434
Category : Science
Languages : en
Pages : 252
Book Description
Scanning Tunneling Microscopy I provides a unique introduction to a novel and fascinating technique that produces beautiful images of nature on an atomic scale. It is the first of three volumes that together offer a comprehensive treatment of scanning tunneling microscopy, its diverse applications, and its theoretical treatment. In this volume the reader will find a detailed description of the technique itself and of its applications to metals, semiconductors, layered materials, adsorbed molecules and superconductors. In addition to the many representative results reviewed, extensive references to original work will help to make accessible the vast body of knowledge already accumulated in this field.
Publisher: Springer Science & Business Media
ISBN: 3642973434
Category : Science
Languages : en
Pages : 252
Book Description
Scanning Tunneling Microscopy I provides a unique introduction to a novel and fascinating technique that produces beautiful images of nature on an atomic scale. It is the first of three volumes that together offer a comprehensive treatment of scanning tunneling microscopy, its diverse applications, and its theoretical treatment. In this volume the reader will find a detailed description of the technique itself and of its applications to metals, semiconductors, layered materials, adsorbed molecules and superconductors. In addition to the many representative results reviewed, extensive references to original work will help to make accessible the vast body of knowledge already accumulated in this field.
In-situ Spectroscopy in Heterogeneous Catalysis
Author: James F. Haw
Publisher: Wiley-VCH Verlag GmbH
ISBN:
Category : Science
Languages : en
Pages : 296
Book Description
"Not using in-situ methods to examine catalytic processes is like studying a life with access only to the prenatal and postmortem states." This quote from the world renowned specialist in the field of in situ methods, Gabor A. Somorjai, clearly emphasizes the importance of these techniques in understanding heterogeneous catalysis - a type of chemical reaction used nowadays for most chemically produced supplies and fuels. Yet the fundamental mechanisms are often still not completely understood. Many of the leading scientists in the field have contributed to this book which provides an overview of the most varied spectroscopic and related methods for studying catalytic structures and their functions during a chemical reaction. While primarily written for users of these methods, this is also a valuable aid to interpreting the phenomena observed. Indispensable for everyone working in the field.
Publisher: Wiley-VCH Verlag GmbH
ISBN:
Category : Science
Languages : en
Pages : 296
Book Description
"Not using in-situ methods to examine catalytic processes is like studying a life with access only to the prenatal and postmortem states." This quote from the world renowned specialist in the field of in situ methods, Gabor A. Somorjai, clearly emphasizes the importance of these techniques in understanding heterogeneous catalysis - a type of chemical reaction used nowadays for most chemically produced supplies and fuels. Yet the fundamental mechanisms are often still not completely understood. Many of the leading scientists in the field have contributed to this book which provides an overview of the most varied spectroscopic and related methods for studying catalytic structures and their functions during a chemical reaction. While primarily written for users of these methods, this is also a valuable aid to interpreting the phenomena observed. Indispensable for everyone working in the field.