Theofanis N. Kitsopoulos
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View article: An Experimental Benchmark for the Barrier Height of an On-Surface Reaction: Hydrogen Oxidation on Pt(332)
An Experimental Benchmark for the Barrier Height of an On-Surface Reaction: Hydrogen Oxidation on Pt(332) Open
Developing predictive theories for the rates of reactions between surface-bound molecules is a central challenge to understanding many important phenomena including: heterogeneous catalysis, electrocatalysis, nanofabrication, and corrosion…
View article: The Mechanism and Rate-Determining Step of Catalytic Ammonia Oxidation on Pd(332) at High Temperatures
The Mechanism and Rate-Determining Step of Catalytic Ammonia Oxidation on Pd(332) at High Temperatures Open
Despite its immense practical importance in industrial production of nitric acid, the mechanisms of catalytic ammonia oxidation on platinum group metals remain controversial. In this work, we employ velocity-resolved kinetics to study ammo…
View article: An ion-imaging detector for high count rates
An ion-imaging detector for high count rates Open
The emergence of high-power ionizing light sources with repetition rates greater than 100 kHz promises vastly improved data acquisition times for electron and ion imaging experiments; however, optimal means to record ion images at high ave…
View article: Multi-mass velocity-resolved kinetics of surface reactions at 100 kHz acquisition rate
Multi-mass velocity-resolved kinetics of surface reactions at 100 kHz acquisition rate Open
Velocity-resolved kinetics (VRK) employs a pulsed molecular beam that initiates reactions at a surface and a pulsed ionization-laser that detects desorbed products, exploiting ion-imaging-based, velocity-sensitive detection to derive the p…
View article: Thermal Rates and High-Temperature Tunneling from Surface Reaction Dynamics and First-Principles
Thermal Rates and High-Temperature Tunneling from Surface Reaction Dynamics and First-Principles Open
Studying dynamics of the dissociative adsorption and recombinative desorption of hydrogen on copper surfaces has shaped our atomic-scale understanding of surface chemistry, yet experimentally determining the thermal rates for these process…
View article: Cooperative adsorbate binding catalyzes high-temperature hydrogen oxidation on palladium
Cooperative adsorbate binding catalyzes high-temperature hydrogen oxidation on palladium Open
Atomic-scale structures that account for the acceleration of reactivity by heterogeneous catalysts often form only under reaction conditions of high temperatures and pressures, making them impossible to observe with low-temperature, ultra-…
View article: Identification of reaction intermediates in the decomposition of formic acid on Pd
Identification of reaction intermediates in the decomposition of formic acid on Pd Open
We report an approach to identify intermediates for the formic acid decomposition reaction on Pd(111) and Pd(332) based on accurate measurements of isotopologue specific thermal reaction rates.
View article: Binding Energy and Diffusion Barrier of Formic Acid on Pd(111)
Binding Energy and Diffusion Barrier of Formic Acid on Pd(111) Open
Velocity-resolved kinetics is used to measure the thermal rate of formic acid desorption from Pd(111) between 228 and 273 K for four isotopologues: HCOOH, HCOOD, DCOOH, DCOOD. Upon molecular adsorption, formic acid undergoes decomposition …
View article: Steric Hindrance of NH<sub>3</sub> Diffusion on Pt(111) by Co-Adsorbed O-Atoms
Steric Hindrance of NH<sub>3</sub> Diffusion on Pt(111) by Co-Adsorbed O-Atoms Open
A detailed velocity-resolved kinetics study of NH3 thermal desorption rates from p(2 × 2) O/Pt(111) is presented. We find a large reduction in the NH3 desorption rate due to adsorption of O-atoms on Pt(111). A physical model describing the…
View article: Adsorption and Absorption Energies of Hydrogen with Palladium
Adsorption and Absorption Energies of Hydrogen with Palladium Open
Thermal recombinative desorption rates of HD on Pd(111) and Pd(332) are reported from transient kinetic experiments performed between 523 and 1023 K. A detailed kinetic model accurately describes the competition between recombination of su…
View article: Quantum effects in thermal reaction rates at metal surfaces
Quantum effects in thermal reaction rates at metal surfaces Open
There is wide interest in developing accurate theories for predicting rates of chemical reactions that occur at metal surfaces, especially for applications in industrial catalysis. Conventional methods contain many approximations that lack…
View article: Velocity‐resolved Laser‐induced Desorption for Kinetics on Surface Adsorbates
Velocity‐resolved Laser‐induced Desorption for Kinetics on Surface Adsorbates Open
Invited for this month's cover are the groups of Alec M. Wodtke at the Georg‐August University in Göttigen (Germany) and at the University of Crete (Greece). The cover picture shows ammonia (NH 3 ) molecules adsorbed on an atomically flat …
View article: Cover Picture: Velocity‐resolved Laser‐induced Desorption for Kinetics on Surface Adsorbates (Chem. Methods 5/2022)
Cover Picture: Velocity‐resolved Laser‐induced Desorption for Kinetics on Surface Adsorbates (Chem. Methods 5/2022) Open
The Front Cover shows ammonia molecules adsorbed on an atomically flat platinum surface. An ultra-short laser pulse hits the surface and heats up the metal electron rapidly to several thousand Kelvin within a few 100fs. This high electroni…
View article: Velocity‐resolved Laser‐induced Desorption for Kinetics on Surface Adsorbates
Velocity‐resolved Laser‐induced Desorption for Kinetics on Surface Adsorbates Open
Most experimental methods for studying the kinetics of surface reactions – for example, temperature programmed desorption (TPD), molecular beam relaxation spectrometry (MBRS) and velocity‐resolved kinetics (VRK) – employ detection schemes …
View article: Kinetics of NH<sub>3</sub> Desorption and Diffusion on Pt: Implications for the Ostwald Process
Kinetics of NH<sub>3</sub> Desorption and Diffusion on Pt: Implications for the Ostwald Process Open
We report accurate time-resolved measurements of NH3 desorption from Pt(111) and Pt(332) and use these results to determine elementary rate constants for desorption from steps, from (111) terrace sites and for diffusion on (111) terraces. …
View article: The Barrier for CO<sub>2</sub> Functionalization to Formate on Hydrogenated Pt
The Barrier for CO<sub>2</sub> Functionalization to Formate on Hydrogenated Pt Open
Understanding heterogeneous catalysis is based on knowing the energetic stability of adsorbed reactants, intermediates, and products as well as the energetic barriers separating them. We report an experimental determination of the barrier …
View article: The puzzle of rapid hydrogen oxidation on Pt(111)
The puzzle of rapid hydrogen oxidation on Pt(111) Open
We have known for over 200 years that hydrogen undergoes rapid oxidation to water on Pt catalysts; yet the reaction mechanism remains unclear. Here, we report high temporal resolution measurements of the production rate of H2O from hydroge…
View article: Adsorbate modification of electronic nonadiabaticity: H atom scattering from <i>p</i>(2 × 2) O on Pt(111)
Adsorbate modification of electronic nonadiabaticity: H atom scattering from <i>p</i>(2 × 2) O on Pt(111) Open
We report inelastic differential scattering experiments for energetic H and D atoms colliding at a Pt(111) surface with and without adsorbed O atoms. Dramatically, more energy loss is seen for scattering from the Pt(111) surface compared t…
View article: NO Binding Energies to and Diffusion Barrier on Pd Obtained with Velocity-Resolved Kinetics
NO Binding Energies to and Diffusion Barrier on Pd Obtained with Velocity-Resolved Kinetics Open
We report nitric oxide (NO) desorption rates from Pd(111) and Pd(332) surfaces measured with velocity-resolved kinetics. The desorption rates at the surface temperatures from 620 to 800 K span more than 3 orders of magnitude, and competing…
View article: Measuring Transient Reaction Rates\nfrom Nonstationary Catalysts
Measuring Transient Reaction Rates\nfrom Nonstationary Catalysts Open
Up\nto now, methods\nfor measuring rates of reactions on catalysts required long measurement\ntimes involving signal averaging over many experiments. This imposed\na requirement that the catalyst return to its original state at the\nend of…
View article: Measuring Transient Reaction Rates from Nonstationary Catalysts
Measuring Transient Reaction Rates from Nonstationary Catalysts Open
Up to now, the methods available for measuring the rate constants of reactions taking place on heterogeneous catalysts require that the catalyst be stable over long measurement times. But catalyst are often non-stationary, they may become …
View article: Probing the Effect of Surface Strain on CO Binding to Pd Thin Films
Probing the Effect of Surface Strain on CO Binding to Pd Thin Films Open
We report measurements to investigate the effects of mechanical strain on the binding energy of carbon monoxide (CO) on the (111) surface of a 16 nm thin film of palladium (Pd) grown on rutile titanium dioxide (r-TiO2). The lattice mismatc…
View article: Velocity-resolved kinetics of site-specific carbon monoxide oxidation on platinum surfaces
Velocity-resolved kinetics of site-specific carbon monoxide oxidation on platinum surfaces Open
Catalysts are widely used to increase reaction rates. They function by stabilizing the transition state of the reaction at their active site, where the atomic arrangement ensures favourable interactions 1 . However, mechanistic understandi…
View article: Ion and velocity map imaging for surface dynamics and kinetics
Ion and velocity map imaging for surface dynamics and kinetics Open
We describe a new instrument that uses ion imaging to study molecular beam-surface scattering and surface desorption kinetics, allowing independent determination of both residence times on the surface and scattering velocities of desorbing…
View article: Assessment of UVA-Riboflavin Corneal Cross-Linking Using Small Amplitude Oscillatory Shear Measurements
Assessment of UVA-Riboflavin Corneal Cross-Linking Using Small Amplitude Oscillatory Shear Measurements Open
We report a simple and accurate methodology for quantifying the effects of cross-linking on porcine corneas treated with the Dresden protocol by means of SAOS measurements in the linear regime. The measured dynamic moduli, elastic and visc…