1,119 research outputs found

    Теоретико-методологічні засади адаптивного інноваційного розвитку

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    Подано визначення змісту управління адаптивним інноваційним розвитком, заснованого на використанні його здібностей до трансформації з урахуванням особливостей зовнішнього та внутрішнього середовища суб’єкта сукупності дій, необхідних для здійснення впливу на процеси в усіх сферах управління, що забезпечує інноваційну, організаційно-управлінську, технічну, фінансову та кадрову стійкість. Ключові слова: інновації, інноваційний розвиток, адаптація, адаптивність, механізм, система, процес.Представлено определение содержания управления адаптивным инновационным развитием, основанным на использовании его способностей к трансформации с учетом особенностей внешней и внутренней среды субъекта совокупности действий, необходимых для осуществления влияния на процессы во всех областях управления, обеспечивающих инновационную, организационно-управленческую, техническую, финансовую и кадровую устойчивость. Ключевые слова: инновации, инновационное развитие, адаптация, адаптивность, механизм, система, процесс.The paper presents the definition of management of adaptive innovation-based development that is based on the use of its ability to transform in view of external and internal environment of the subject of actions necessary for making influence on the processes in all areas of management, providing innovative, organizational, administrative, technical, financial and personnel stability of the production company. Keywords: innovation, innovation-based development, adaptation, adaptability, mechanism, system, process

    Activation and dissociation of CO2 on the (001), (011), and (111) surfaces of mackinawite (FeS): a dispersion-corrected DFT study

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    Iron sulfide minerals, including mackinawite (FeS), are relevant in origin of life theories, due to their potential catalytic activity towards the reduction and conversion of carbon dioxide (CO2) to organic molecules, which may be applicable to the production of liquid fuels and commodity chemicals. However, the fundamental understanding of CO2 adsorption, activation, and dissociation on FeS surfaces remains incomplete. Here, we have used density functional theory calculations, corrected for long-range dispersion interactions (DFT-D2), to explore various adsorption sites and configurations for CO2 on the low-index mackinawite (001), (110), and (111) surfaces. We found that the CO2 molecule physisorbs weakly on the energetically most stable (001) surface but adsorbs relatively strongly on the (011) and (111) FeS surfaces, preferentially at Fe sites. The adsorption of the CO2 on the (011) and (111) surfaces is shown to be characterized by significant charge transfer from surface Fe species to the CO2 molecule, which causes a large structural transformation in the molecule (i.e., forming a negatively charged bent CO2−δ species, with weaker C—O confirmed via vibrational frequency analyses). We have also analyzed the pathways for CO2 reduction to CO and O on the mackinawite (011) and (111) surfaces. CO2 dissociation is calculated to be slightly endothermic relative to the associatively adsorbed states, with relatively large activation energy barriers of 1.25 eV and 0.72 eV on the (011) and (111) surfaces, respectively

    DFT-D2 simulations of water adsorption and dissociation on the low-index surfaces of mackinawite (FeS)

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    The adsorption and dissociation of water on mackinawite (layered FeS) surfaces were studied using dispersion-corrected density functional theory (DFT-D2) calculations. The catalytically active sites for H2O and its dissociated products on the FeS {001}, {011}, {100}, and {111} surfaces were determined, and the reaction energetics and kinetics of water dissociation were calculated using the climbing image nudged elastic band technique. Water and its dissociation products are shown to adsorb more strongly onto the least stable FeS{111} surface, which presents low-coordinated cations in the surface, and weakest onto the most stable FeS{001} surface. The adsorption energies decrease in the order FeS{111} > FeS{100} > FeS{011} > FeS{001}. Consistent with the superior reactivity of the FeS{111} surface towards water and its dissociation products, our calculated thermochemical energies and activation barriers suggest that the water dissociation reaction will take place preferentially on the FeS nanoparticle surface with the {111} orientation. These findings improve our understanding of how the different FeS surface structures and the relative stabilities dictate their reactivity towards water adsorption and dissociation

    Surface oxygen Vacancies on Reduced Co<sub>3</sub>O<sub>4</sub>(100): Superoxide Formation and Ultra-Low-Temperature CO Oxidation

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    The activation of molecular oxygen is a fundamental step in almost all catalytic oxidation reactions.We have studied this topic and the role of surface vacancies for Co3O4(100) films with a synergistic combination of experimental and theoretical methods. We show that the as-prepared surface is Blayer terminated and that mild reduction produces oxygen single and double vacancies in this layer. Oxygen adsorption experiments clearly reveal different superoxide species below room temperature. The superoxide desorbs below ca. 120 K from a vacancy-free surface and is not active for CO oxidation while superoxide on a surface with oxygen vacancies is stable up to ca. 270 K and can oxidize CO already at the low temperature of 120 K. The vacancies are not refilled by oxygen from the superoxide, which makes them suitable for long-term operation. Our joint experimental/theoretical effort highlights the relevance of surface vacancies in catalytic oxidation reactions

    Surface oxygen Vacancies on Reduced Co<sub>3</sub>O<sub>4</sub>(100): Superoxide Formation and Ultra-Low-Temperature CO Oxidation

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    The activation of molecular oxygen is a fundamental step in almost all catalytic oxidation reactions.We have studied this topic and the role of surface vacancies for Co3O4(100) films with a synergistic combination of experimental and theoretical methods. We show that the as-prepared surface is Blayer terminated and that mild reduction produces oxygen single and double vacancies in this layer. Oxygen adsorption experiments clearly reveal different superoxide species below room temperature. The superoxide desorbs below ca. 120 K from a vacancy-free surface and is not active for CO oxidation while superoxide on a surface with oxygen vacancies is stable up to ca. 270 K and can oxidize CO already at the low temperature of 120 K. The vacancies are not refilled by oxygen from the superoxide, which makes them suitable for long-term operation. Our joint experimental/theoretical effort highlights the relevance of surface vacancies in catalytic oxidation reactions

    Adatom Bonding Sites in a Nickel-Fe<sub>3</sub>O<sub>4</sub>(001) Single-Atom Model Catalyst and O<sub>2</sub> Reactivity Unveiled by Surface Action Spectroscopy with Infrared Free-Electron Laser Light

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    Single-atom (SA) catalysis presently receives much attention with its promise to decrease the cost of the active material while increasing the catalyst’s performance. However, key details such as the exact location of SA species and their stability are often unclear due to a lack of atomic level information. Here, we show how vibrational spectra measured with surface action spectroscopy (SAS) and density functional theory (DFT) simulations can differentiate between different adatom binding sites and determine the location of Ni and Au single atoms on Fe3O4. We reveal that Ni and Au adatoms selectively bind to surface oxygen ions which are octahedrally coordinated to Fe ions. In addition, we find that the Ni adatoms can activate O2 to superoxide in contrast to the bare surface and Ni in subsurface positions. Overall, we unveil the advantages of combining SAS and DFT for improving the understanding of single-atom catalysts

    Adatom Bonding Sites in a Nickel-Fe<sub>3</sub>O<sub>4</sub>(001) Single-Atom Model Catalyst and O<sub>2</sub> Reactivity Unveiled by Surface Action Spectroscopy with Infrared Free-Electron Laser Light

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    Single-atom (SA) catalysis presently receives much attention with its promise to decrease the cost of the active material while increasing the catalyst’s performance. However, key details such as the exact location of SA species and their stability are often unclear due to a lack of atomic level information. Here, we show how vibrational spectra measured with surface action spectroscopy (SAS) and density functional theory (DFT) simulations can differentiate between different adatom binding sites and determine the location of Ni and Au single atoms on Fe3O4. We reveal that Ni and Au adatoms selectively bind to surface oxygen ions which are octahedrally coordinated to Fe ions. In addition, we find that the Ni adatoms can activate O2 to superoxide in contrast to the bare surface and Ni in subsurface positions. Overall, we unveil the advantages of combining SAS and DFT for improving the understanding of single-atom catalysts

    Surface Segregation in CuNi Nanoparticle Catalysts During CO<sub>2</sub> Hydrogenation: The Role of CO in the Reactant Mixture

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    Surface segregation and restructuring in size-selected CuNi nanoparticles were investigated via near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) at various temperatures in different gas environments. Particularly in focus were structural and morphological changes occurring under CO2 hydrogenation conditions in the presence of carbon monoxide (CO) in the reactant gas mixture. Nickel surface segregation was observed when only CO was present as adsorbate. The segregation trend is inverted in a reaction gas mixture consisting of CO2, H2, and CO, resulting in an increase of copper concentration on the surface. Density functional theory calculations attributed the inversion of the segregation trend to the formation of a stable intermediate on the nanocatalyst surface (CH3O) in the CO-containing reactant mixture, which modifies the nickel segregation energy, thus driving copper to the surface. The promoting role of CO for the synthesis of methanol was demonstrated by catalytic characterization measurements of silica-supported CuNi NPs in a fixed-bed reactor, revealing high methanol selectivity (over 85%) at moderate pressures (20 bar). The results underline the important role of intermediate reaction species in determining the surface composition of bimetallic nanocatalysts and help understand the effect of CO cofeed on the properties of CO2 hydrogenation catalysts
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