The Experts below are selected from a list of 56331 Experts worldwide ranked by ideXlab platform
Shunfang Li - One of the best experts on this subject based on the ideXlab platform.
-
interplay between the spin selection rule and frontier Orbital Theory in o2 activation and co oxidation by single atom sized catalysts on tio2 110
Physical Chemistry Chemical Physics, 2016Co-Authors: Shunfang Li, Xingju Zhao, Zhenyu ZhangAbstract:Exploration of the catalytic activity of low-dimensional transition metal (TM) or noble metal catalysts is a vital subject of modern materials science because of their instrumental role in numerous industrial applications. Recent experimental advances have demonstrated the utilization of single atoms on different substrates as effective catalysts, which exhibit amazing catalytic properties such as more efficient catalytic performance and higher selectivity in chemical reactions as compared to their nanostructured counterparts; however, the underlying microscopic mechanisms operative in these single atom catalysts still remain elusive. Based on first-principles calculations, herein, we present a comparative study of the key kinetic rate processes involved in CO oxidation using a monomer or dimer of two representative TMs (Pd and Ni) on defective TiO2(110) substrates (TMn@TiO2(110), n = 1, 2) to elucidate the underlying mechanism of single-atom catalysis. We reveal that the O2 activation rates of the single atom TM catalysts deposited on TiO2(110) are governed cooperatively by the classic spin-selection rule and the well-known frontier Orbital Theory (or generalized d-band picture) that emphasizes the energy gap between the frontier Orbitals of the TM catalysts and O2 molecule. We further illuminate that the subsequent CO oxidation reactions proceed via the Langmuir–Hinshelwood mechanism with contrasting reaction barriers for the Pd monomer and dimer catalysts. These findings not only provide an explanation for existing observations of distinctly different catalytic activities of Pd@TiO2(110) and Pd2@TiO2(110) [Kaden et al., Science, 2009, 326, 826–829] but also shed new insights into future utilization and optimization of single-atom catalysis.
Paul W Ayers - One of the best experts on this subject based on the ideXlab platform.
-
a proposal for an extended dual descriptor a possible solution when frontier molecular Orbital Theory fails
Physical Chemistry Chemical Physics, 2013Co-Authors: Vincent Tognetti, Paul W Ayers, Christophe Morell, Laurent Joubert, Henry ChermetteAbstract:In this paper, we introduce new local descriptors in the framework of Conceptual Density Functional Theory. They can be considered as an extension of the dual descriptor [Morell et al., J. Phys. Chem. A, 2005, 109, 205]. These indices are particularly suited for the discrimination between electrophilic and nucleophilic sites inside a molecule. They are computed using the densities of the electronic excited states, giving a picture of the polarization of the electron density induced by the approach of a reactant. Links with the linear-response function are discussed, and the first examples of applications are given, highlighting how these new descriptors can be used in practice for reactivity studies. It has been found that this extension of the dual descriptor can handle tricky cases, such as nitrobenzene or isoquinoline, for which Frontier Molecular Orbital Theory fails.
-
conceptual density functional Theory for general chemical reactions including those that are neither charge nor frontier Orbital controlled 2 application to molecules where frontier molecular Orbital Theory fails
Journal of Chemical Theory and Computation, 2007Co-Authors: James S M Anderson, Jan Melin, Paul W AyersAbstract:This paper examines cases where frontier molecular Orbital Theory is known to fail, specifically electrophilic aromatic substitution reactions on isoquinoline and borazarophenanthrenes. While we are able to explain the experimental regioselectivity preferences for isoquinoline without too much difficulty, describing the regioselectivity of the borazarophenanthrenes is much more challenging. This is attributed to the fact that these molecules lie between the electrostatic (or charge) control and electron-transfer (or frontier-Orbital) control paradigms. These molecules can, however, be described using the general-purpose reactivity indicator introduced in the first paper of this series. The variation of the general-purpose reactivity indicator with respect to the parameters is readily summed up using what we term “reactivity transition tables”, which provide a compact summary of which products form under different reaction conditions. For the otherwise problematic molecules considered here, the new reactiv...
Kazunari Yoshizawa - One of the best experts on this subject based on the ideXlab platform.
-
understanding single molecule parallel circuits on the basis of frontier Orbital Theory
The Journal of Physical Chemistry, 2020Co-Authors: Kazuki Okazawa, Yuta Tsuji, Kazunari YoshizawaAbstract:In electronic devices, as the number of paths connecting source and drain electrodes increases, the conductance of the device will also increase. However, this is not always the case on the nanoscale. According to the current superposition law at work in the macroscopic electrical circuits, doubling the number of paths should double the conductance, but when such paths are examined on the basis of the frontier Orbital Theory for nanoscale electrical circuits, more complex scenarios arise. When the number of paths in a molecule is doubled, the conductance may get more than doubled, remain unchanged, or even be reduced. We propose a classification of conducting systems falling into each of these scenarios with the help of aromaticity. The present work involves a theoretical study using the nonequilibrium Green’s function that shows that these varying outcomes are closely related to the presence or absence of aromatic rings. This work serves to characterize molecular conductance characteristics based on frontier Orbital Theory, Orbital interactions, and a local transmission concept. Some discrete mathematical aspects of the relationship between atom connectivity and electron conductivity are also described.
Zhenyu Zhang - One of the best experts on this subject based on the ideXlab platform.
-
interplay between the spin selection rule and frontier Orbital Theory in o2 activation and co oxidation by single atom sized catalysts on tio2 110
Physical Chemistry Chemical Physics, 2016Co-Authors: Shunfang Li, Xingju Zhao, Zhenyu ZhangAbstract:Exploration of the catalytic activity of low-dimensional transition metal (TM) or noble metal catalysts is a vital subject of modern materials science because of their instrumental role in numerous industrial applications. Recent experimental advances have demonstrated the utilization of single atoms on different substrates as effective catalysts, which exhibit amazing catalytic properties such as more efficient catalytic performance and higher selectivity in chemical reactions as compared to their nanostructured counterparts; however, the underlying microscopic mechanisms operative in these single atom catalysts still remain elusive. Based on first-principles calculations, herein, we present a comparative study of the key kinetic rate processes involved in CO oxidation using a monomer or dimer of two representative TMs (Pd and Ni) on defective TiO2(110) substrates (TMn@TiO2(110), n = 1, 2) to elucidate the underlying mechanism of single-atom catalysis. We reveal that the O2 activation rates of the single atom TM catalysts deposited on TiO2(110) are governed cooperatively by the classic spin-selection rule and the well-known frontier Orbital Theory (or generalized d-band picture) that emphasizes the energy gap between the frontier Orbitals of the TM catalysts and O2 molecule. We further illuminate that the subsequent CO oxidation reactions proceed via the Langmuir–Hinshelwood mechanism with contrasting reaction barriers for the Pd monomer and dimer catalysts. These findings not only provide an explanation for existing observations of distinctly different catalytic activities of Pd@TiO2(110) and Pd2@TiO2(110) [Kaden et al., Science, 2009, 326, 826–829] but also shed new insights into future utilization and optimization of single-atom catalysis.
Henry Chermette - One of the best experts on this subject based on the ideXlab platform.
-
a proposal for an extended dual descriptor a possible solution when frontier molecular Orbital Theory fails
Physical Chemistry Chemical Physics, 2013Co-Authors: Vincent Tognetti, Paul W Ayers, Christophe Morell, Laurent Joubert, Henry ChermetteAbstract:In this paper, we introduce new local descriptors in the framework of Conceptual Density Functional Theory. They can be considered as an extension of the dual descriptor [Morell et al., J. Phys. Chem. A, 2005, 109, 205]. These indices are particularly suited for the discrimination between electrophilic and nucleophilic sites inside a molecule. They are computed using the densities of the electronic excited states, giving a picture of the polarization of the electron density induced by the approach of a reactant. Links with the linear-response function are discussed, and the first examples of applications are given, highlighting how these new descriptors can be used in practice for reactivity studies. It has been found that this extension of the dual descriptor can handle tricky cases, such as nitrobenzene or isoquinoline, for which Frontier Molecular Orbital Theory fails.
