Trimetallic NiCoM catalysts (M = Mn,Fe, Cu) for methane conversion into synthesis gas

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Real-Space Interpretation of Interatomic Charge Transfer and Electron Exchange Effects by Combining Static and Kinetic Potentials and Associated Vector Fields**

Intricate behaviour of one-electron potentials from the Euler equation for electron density and corresponding gradient force fields in crystals was studied. Channels of locally enhanced kinetic potential and corresponding saddle Lagrange points were found between chemically bonded atoms. Superposition of electrostatic and kinetic potentials and electron density allowed partitioning any molecules and crystals into atomic - and potential-based -basins; -basins explicitly account for the electron exchange effect, which is missed for -ones. Phenomena of interatomic charge transfer and related electron exchange were explained in terms of space gaps between zero-flux surfaces of - and -basins. The gap between - and -basins represents the charge transfer, while the gap between - and -basins is a real-space manifestation of sharing the transferred electrons caused by the static exchange and kinetic effects as a response against the electron transfer. The regularity describing relative positions of -, -, and - basin boundaries between interacting atoms was proposed. The position of -boundary between - and -ones within an electron occupier atom determines the extent of transferred electron sharing. The stronger an H⋅⋅⋅O hydrogen bond is, the deeper hydrogen atom's -basin penetrates oxygen atom's -basin, while for covalent bonds a -boundary closely approaches a -one indicating almost complete sharing of the transferred electrons. In the case of ionic bonds, the same region corresponds to electron pairing within the -basin of an electron occupier atom.     

Metastable states in high carbon C–(Fe,Ni, Co) films obtained by three-electrode ion-plasma sputtering

Abstract

The effect of ion-plasma deposition on the structure of high-carbon films (at. %) Fe–(20–84) % С, Co–(5–52) % С, Ni–(7–61) % С was investigated. The lattice periods and crystallite sizes of nonequilibrium phases in the as-deposited state and after heating are determined. The temperatures of the beginning and end of the decay of metastable phases during heating at a constant speed are established. The transition from an amorphous to an equilibrium crystalline state in Fe–C films passes through the stage of formation and subsequent decomposition of an intermediate, metastable hcp phase of variable composition. The electrical and hysteretic magnetic properties of the films were measured in the as-deposited state and after heat treatment. The compositions and conditions for producing films with low values of the temperature coefficient of electrical resistance and high coercive force are established. Thus, high-carbon films of Ni–61% C in the as-depoteted state and Fe–69% C films after heating to 900?K are characterized by small TCR values (± 10^?6 К^?1) over a wide temperature range.     

Highly porous polymeric sponges for oil sorption

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Modified and environmentally friendly oxidation of phosphorane ylides to vicinal tricarbonyls using unsupported moist Oxone in dichloromethane

Abstract

Modified and eco-friendly oxidation of phosphorane ylides to the corresponding vicinal tricarbonyls (VTC) using unsupported moist Oxone in dichloromethane at room temperature is described. This green oxidation protocol is simple, mild, and highly efficient to operate, and allowing a chemoselective preparation of VTC from various phosphorane ylides without tedious workup procedures of extraction/drying process in excellent yields.     

Influence of Potassium Metal-Support Interactions on Dendrite Growth

Combined synchrotron X-ray nanotomography imaging, cryogenic electron microscopy (cryo-EM) and modeling elucidate how potassium (K) metal-support energetics influence electrodeposit microstructure. Three model supports are employed: O-functionalized carbon cloth (potassiophilic, fully-wetted), non-functionalized cloth and Cu foil (potassiophobic, nonwetted). Nanotomography and focused ion beam (cryo-FIB) cross-sections yield complementary three-dimensional (3D) maps of cycled electrodeposits. Electrodeposit on potassiophobic support is a triphasic sponge, with fibrous dendrites covered by solid electrolyte interphase (SEI) and interspersed with nanopores (sub-10 nm to 100 nm scale). Lage cracks and voids are also a key feature. On potassiophilic support, the deposit is dense and pore-free, with uniform surface and SEI morphology. Mesoscale modeling captures the critical role of substrate-metal interaction on K metal film nucleation and growth, as well as the associated stress state.     

The Nephelauxetic Effect Becomes an Important Design Factor for Photoactive First-Row Transition Metal Complexes

The expansion of d-orbitals as a result of metal-ligand bond covalence, the so-called nephelauxetic effect, is a well-established concept of coordination chemistry, yet its importance for the design of new photoactive complexes based on first-row transition metals is only beginning to be recognized. Until recently, much focus has been on optimizing the ligand field strength, coordination geometries, and molecular rigidity, but now it becomes evident that the nephelauxetic effect can be a game changer regarding the photophysical properties of 3d metal complexes in solution at room temperature. In Cr^III and Mn^IV complexes with the d³ valence electron configuration, the nephelauxetic effect was exploited to shift the well-known ruby-like red luminescence to the near-infrared spectral region. In Fe^II and Co^III complexes with the low-spin d⁶ electron configuration, charge-transfer excited states were stabilized with respect to detrimental metal-centered excited states, to improve their properties and to enhance their application potential. In isoelectronic (3d⁶) isocyanide complexes of Cr⁰ and Mn^I, the nephelauxetic effect is likely at play as well, enabling luminescence and other favorable photoreactivity. This minireview illustrates the broad applicability of the nephelauxetic effect in tailoring the photophysical and photochemical properties of new coordination compounds made from abundant first-row transition metals.     

Highly Cooperative CO2 Adsorption via a Cation Crowding Mechanism on a Cesium-Exchanged Phillipsite Zeolite

An understanding of the CO₂ adsorption mechanisms on small-pore zeolites is of practical importance in the development of more efficient adsorbents for the separation of CO₂ from N₂ or CH₄. Here we report that the CO₂ isotherms at 25–75 °C on cesium-exchanged phillipsite zeolite with a Si/Al ratio of 2.5 (Cs-PHI-2.5) are characterized by a rectilinear step shape: limited uptake at low CO₂ pressure (P_CO2) is followed by highly cooperative uptake at a critical pressure, above which adsorption rapidly approaches capacity (2.0 mmol g⁻¹). Structural analysis reveals that this isotherm behavior is attributed to the high concentration and large size of Cs⁺ ions in dehydrated Cs-PHI-2.5. This results in Cs⁺ cation crowding and subsequent dispersal at a critical loading of CO₂, which allows the PHI framework to relax to its wide pore form and enables its pores to fill with CO₂ over a very narrow range of P_CO2. Such a highly cooperative phenomenon has not been observed for other zeolites.