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Full-Text Articles in Engineering
Sum Frequency Generation Vibrational Spectroscopy Of Pyridine Hydrogenation On Platinum Nanoparticles, Kaitlin M. Bratlie, Kyriakos Komvopoulos, Gabor A. Somorjai
Sum Frequency Generation Vibrational Spectroscopy Of Pyridine Hydrogenation On Platinum Nanoparticles, Kaitlin M. Bratlie, Kyriakos Komvopoulos, Gabor A. Somorjai
Kaitlin M. Bratlie
Pyridine hydrogenation in the presence of a surface monolayer consisting of cubic Pt nanoparticles stabilized by tetradecyltrimethylammonium bromide (TTAB) was investigated by sum frequency generation (SFG) vibrational spectroscopy using total internal reflection (TIR) geometry. TIR-SFG spectra analysis revealed that a pyridinium cation (C5H5NH+) forms during pyridine hydrogenation on the Pt nanoparticle surface, and the NH group in the C5H5NH+ cation becomes more hydrogen bound with the increase of the temperature. In addition, the surface coverage of the cation decreases with the increase of the temperature. An important contribution of this study is the in situ identification of reaction intermediates adsorbed …
Platinum Nanoparticle Shape Effects On Benzene Hydrogenation Selectivity, Kaitlin M. Bratlie, Hyunjoo Lee, Kyriakos Komvopoulos, Peidong Yang, Gabor A. Somorjai
Platinum Nanoparticle Shape Effects On Benzene Hydrogenation Selectivity, Kaitlin M. Bratlie, Hyunjoo Lee, Kyriakos Komvopoulos, Peidong Yang, Gabor A. Somorjai
Kaitlin M. Bratlie
Benzene hydrogenation was investigated in the presence of a surface monolayer consisting of Pt nanoparticles of different shapes (cubic and cuboctahedral) and tetradecyltrimethylammonium bromide (TTAB). Infrared spectroscopy indicated that TTAB binds to the Pt surface through a weak C-HâââPt bond of the alkyl chain. The catalytic selectivity was found to be strongly affected by the nanoparticle shape. Both cyclohexane and cyclohexene product molecules were formed on cuboctahedral nanoparticles, whereas only cyclohexane was produced on cubic nanoparticles. These results are the same as the product selectivities obtained on Pt(111) and Pt(100) single crystals in earlier studies. The apparent activation energy for …
A Sum Frequency Generation Vibrational Spectroscopic Study Of The Adsorption And Reactions Of C6 Hydrocarbons At High Pressures On Pt(100), Kaitlin M. Bratlie, Gabor A. Somorjai
A Sum Frequency Generation Vibrational Spectroscopic Study Of The Adsorption And Reactions Of C6 Hydrocarbons At High Pressures On Pt(100), Kaitlin M. Bratlie, Gabor A. Somorjai
Kaitlin M. Bratlie
Sum frequency generation (SFG) vibrational spectroscopy was used to investigate the adsorption geometries and surface reactions of various C6 hydrocarbons (n-hexane, 2-methylpentane, 3-methylpentane, and 1-hexene) on Pt(100). At 300 K and in the presence of excess hydrogen, n-hexane, 3-methylpentane, and 2-methylpentane adsorb molecularly on Pt(100) mostly in “flat-lying” conformations. Upon heating the metal surface to 450 K, the molecules underwent dehydrogenation to form new surface species in “standing-up” conformations, such as hexylidyne and metallacyclic species.
Hydrogen And Deuterium Exchange On Pt(111) And Its Poisoning By Carbon Monoxide Studied By Surface Sensitive High-Pressure Techniques, Max Montano, Kaitlin M. Bratlie, Miquel Salmeron, Gabor A. Somorjai
Hydrogen And Deuterium Exchange On Pt(111) And Its Poisoning By Carbon Monoxide Studied By Surface Sensitive High-Pressure Techniques, Max Montano, Kaitlin M. Bratlie, Miquel Salmeron, Gabor A. Somorjai
Kaitlin M. Bratlie
Catalytic hydrogen/deuterium exchange on a platinum (111) single crystal and its poisoning with carbon monoxide was studied using scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), sum frequency generation vibrational spectroscopy (SFG), and mass spectrometry under reaction conditions at pressures in the mTorr to atmospheric range. At 298 K and in the presence of 200 mTorr of hydrogen and 20 mTorr of deuterium the surface is catalytically active, producing HD with activation energy of 5.3 kcal/mol. Addition of 5 mTorr of CO stops the reaction completely. In situ STM images reveal an ordered surface structure of chemisorbed CO. At 353 …
Sum Frequency Generation Vibrational Spectroscopic And High-Pressure Scanning Tunneling Microscopic Studies Of Benzene Hydrogenation On Pt(111), Kaitlin M. Bratlie, Max O. Montano, Lucio D. Flores, Matti Paajanen, Gabor A. Somorjai
Sum Frequency Generation Vibrational Spectroscopic And High-Pressure Scanning Tunneling Microscopic Studies Of Benzene Hydrogenation On Pt(111), Kaitlin M. Bratlie, Max O. Montano, Lucio D. Flores, Matti Paajanen, Gabor A. Somorjai
Kaitlin M. Bratlie
Sum frequency generation (SFG) vibrational spectroscopy and high-pressure scanning tunneling microscopy (HP-STM) have been used in combination for the first time to study a catalytic reaction. These techniques have been able to identify surface intermediates in situ during benzene hydrogenation on a Pt(111) single-crystal surface at Torr pressures.
Structure Effects Of Benzene Hydrogenation Studied With Sum Frequency Generation Vibrational Spectroscopy And Kinetics On Pt(111) And Pt(100) Single-Crystal Surfaces, Kaitlin M. Bratlie, Christopher J. Kliewer, Gabor A. Somorjai
Structure Effects Of Benzene Hydrogenation Studied With Sum Frequency Generation Vibrational Spectroscopy And Kinetics On Pt(111) And Pt(100) Single-Crystal Surfaces, Kaitlin M. Bratlie, Christopher J. Kliewer, Gabor A. Somorjai
Kaitlin M. Bratlie
Sum frequency generation (SFG) surface vibrational spectroscopy and kinetic measurements using gas chromatography have identified at least two reaction pathways for benzene hydrogenation on the Pt(100) and Pt(111) single-crystal surfaces at Torr pressures. Kinetic studies at low temperatures (310-370 K) show that benzene hydrogenation does not proceed through cyclohexene. A Langmuir-Hinshelwood-type rate law for the low-temperature reaction pathway is identified. The rate-determining step for this pathway is the addition of the first hydrogen atom to adsorbed benzene for both single-crystal surfaces, which is verified by the spectroscopic observation of adsorbed benzene at low temperatures on both the Pt(100) and Pt(111) …
Dynamics Of Surface Catalyzed Reactions; The Roles Of Surface Defects, Surface Diffusion, And Hot Electrons, Gabor Somorjai, Kaitlin Bratlie, Max Montano, Jeong Park
Dynamics Of Surface Catalyzed Reactions; The Roles Of Surface Defects, Surface Diffusion, And Hot Electrons, Gabor Somorjai, Kaitlin Bratlie, Max Montano, Jeong Park
Kaitlin M. Bratlie
The mechanism that controls bond breaking at transition metal surfaces has been studied with sum frequency generation (SFG), scanning tunneling microscopy (STM), and catalytic nanodiodes operating under the highpressure conditions. The combination of these techniques permits us to understand the role of surface defects, surface diffusion, and hot electrons in dynamics of surface catalyzed reactions. Sum frequency generation vibrational spectroscopy and kinetic measurements were performed under 1.5 Torr of cyclohexene hydrogenation/dehydrogenation in the presence and absence of H2 and over the temperature range 300-500 K on the Pt(100) and Pt(111) surfaces. The structure specificity of the Pt(100) and Pt(111) surfaces …
In Situ Sum Frequency Generation Vibrational Spectroscopy Observation Of A Reactive Surface Intermediate During High-Pressure Benzene Hydrogenation, Kaitlin M. Bratlie, Lucio D. Flores, Gabor A. Somorjai
In Situ Sum Frequency Generation Vibrational Spectroscopy Observation Of A Reactive Surface Intermediate During High-Pressure Benzene Hydrogenation, Kaitlin M. Bratlie, Lucio D. Flores, Gabor A. Somorjai
Kaitlin M. Bratlie
Sum frequency generation surface vibrational spectroscopy and kinetic measurements using gas chromatography have been used to identify a reactive surface intermediate in situ during hydrogenation of benzene on a Pt(111) single crystal surface at Torr pressures. Upon adsorption at 310 K, both chemisorbed and physisorbed benzene coexist on the surface, a result which has not previously been observed. Kinetic measurements show a linear compensation effect for the production of both cyclohexane and cyclohexene. From these data the isokinetic temperature was identified and correlated to the chemisorbed benzene species, which were probed by means of vibrational spectroscopy. Additionally, chemisorbed benzene was …