Author: Kevin Shao-Lin HwangPublisher:
ISBN:
Category :
Languages : en
Pages : 272
Book Description
Adsorbate Structures and Catalytic Reactions Studied in the Torr Pressure Range by Scanning Tunneling Microscopy
Author: Kevin Shao-Lin HwangPublisher:
ISBN:
Category :
Languages : en
Pages : 272
Book Description
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.
Scanning Tunneling Microscopy in Surface Science, Nanoscience, and Catalysis
Author: Michael BowkerPublisher: John Wiley & Sons
ISBN: 9783527628834
Category : Science
Languages : en
Pages : 258
Book Description
Here, top international authors in the field of STM and surface science present first-class contributions on this hot topic, bringing the reader up to date with the latest developments in this rapidly advancing field. The focus is on the nanoscale, particularly in relation to catalysis, involving developments in our understanding of the nature of the surfaces of oxides and nanoparticulate materials, as well as adsorption, and includes in-situ studies of catalysis on such model materials. Of high interest to practitioners of surface science, nanoscience, STM and catalysis.
High Pressure Scanning Tunneling Microscopy Studies of Adsorbate Structure and Mobility During Catalytic Reactions
Author: David Chi-Wai TangHigh Pressure, High Temperature Scanning Tunneling Microscopy Studies of CO, NO, and 02 on Pt(111) and Rh(111)
Author: Keith Benton RiderEncyclopedia of Interfacial Chemistry
Author: Publisher: Elsevier
ISBN: 0128098945
Category : Science
Languages : en
Pages : 5276
Book Description
Encyclopedia of Interfacial Chemistry: Surface Science and Electrochemistry, Seven Volume Set summarizes current, fundamental knowledge of interfacial chemistry, bringing readers the latest developments in the field. As the chemical and physical properties and processes at solid and liquid interfaces are the scientific basis of so many technologies which enhance our lives and create new opportunities, its important to highlight how these technologies enable the design and optimization of functional materials for heterogeneous and electro-catalysts in food production, pollution control, energy conversion and storage, medical applications requiring biocompatibility, drug delivery, and more. This book provides an interdisciplinary view that lies at the intersection of these fields. Presents fundamental knowledge of interfacial chemistry, surface science and electrochemistry and provides cutting-edge research from academics and practitioners across various fields and global regions
Dissertation Abstracts International
Author: Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 806
Book Description
Dynamics of Surfaces and Reaction Kinetics in Heterogeneous Catalysis
Author: G.F. FromentPublisher: Elsevier
ISBN: 0080530621
Category : Technology & Engineering
Languages : en
Pages : 611
Book Description
Many processes of the chemical industry are based upon heterogeneous catalysis. Two important items of these processes are the development of the catalyst itself and the design and optimization of the reactor. Both aspects would benefit from rigorous and accurate kinetic modeling, based upon information on the working catalyst gained from classical steady state experimentation, but also from studies using surface science techniques, from quantum chemical calculations providing more insight into possible reaction pathways and from transient experimentation dealing with reactions and reactors. This information is seldom combined into a kinetic model and into a quantitative description of the process. Generally the catalytic aspects are dealt with by chemists and by physicists, while the chemical engineers are called upon for mechanical aspects of the reactor design and its control. The symposium "Dynamics of Surfaces and Reaction Kinetics in Heterogeneous Catalysis" aims at illustrating a more global and concerted approach through a number of prestigious keynote lectures and severely screened oral and poster presentations.
Proceedings of the Robert A. Welch Foundation Conferences on Chemical Research
Author: Encyclopedia of Materials
Author: K. H. J. BuschowPublisher:
ISBN:
Category : Materials
Languages : en
Pages : 1096
Book Description
Accompanyind CR-ROM conrtains The Encyclopedia of Materials Science and Technology on a web access disc.