We present a Hubbard-corrected density functional theory (DFT+U) study of the adsorption and reduction reactions of oxygen on the pure and 25% Ca-doped LaMnO3 (LCM25) {100} and {110} surfaces.

The oxo complexes of group VII B are of great interest for their potential toward epoxidation and dihydroxylation. In this work, the mechanisms of oxidation of ethylene by rhenium-oxo complexes of the type LReO3 (L = O(-), Cl, CH3, OCH3, Cp, NPH3) have been explored at the B3LYP/LACVP* level of theory. The activation barriers and reaction energies for the stepwise and concerted addition pathways involving multiple spin states have been computed. In the reaction of LReO3 (L = O(-), Cl, CH3, OCH3, Cp, NPH3) with ethylene, it was found that the concerted [3 + 2] addition pathway on the singlet potential energy surfaces leading to the formation of a dioxylate intermediate is favored over the [2 + 2] addition pathway leading to the formation of a metallaoxetane intermediate and its re-arrangement to form the dioxylate. The activation barrier for the formation of the dioxylate on the singlet PES for the ligands studied is found to follow the order O(-) > CH3 > NPH3 > CH3O(-) > Cl(-) > Cp and the reaction energies follow the order CH3 > O(-) > NPH3 > CH3O(-) > Cl(-) > Cp. On the doublet PES, the [2 + 2] addition leading to the formation the metallaoxetane intermediate is favored over dioxylate formation for the ligands L = CH3, CH3O(-), Cl(-). The activation barriers for the formation of the metallaoxetane intermediate are found to increase for the ligands in the order CH3 < Cl(-) < CH3O(-) while the reaction energies follow the order Cl(-) < CH3O(-) < CH3. The subsequent re-arrangement of the metallaoxetane intermediate to the dioxylate is only feasible in the case of ReO3(OCH3). Of all the complexes studied, the best dioxylating catalyst is ReO3Cp (singlet surface); the best epoxidation catalyst is ReO3Cl (singlet surface); and the best metallaoxetane formation catalyst is ReO3(NPH3) (triplet surface).

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Type-II g-GaN/Sc2CO2 van der Waals heterostructure with electronic properties has potential for nanoelectronics, optoelectronics and photovoltaic device applications.

Photocatalytic water splitting for hydrogen generation utilizing a highly efficient type II van der Waals (vdW) heterostructure is a novel class of materials with highly tunable bandgap energy and band...

The mechanisms of oxidation of ethylene by manganese-oxo complexes of the type MnO3L (L = O(-), Cl, CH3, OCH3, Cp, NPH3) have been explored on the singlet, doublet, triplet and quartet potential energy surfaces at the B3LYP/LACVP* level of theory and the results discussed and compared with those of the technetium and rhenium oxo complexes we reported earlier, thereby drawing group trends in the reactions of this important class of oxidation catalysts. In the reactions of MnO3L (L = O(-), Cl(-), CH3, OCH3, Cp, NPH3) with ethylene, it was found that the formation of the dioxylate intermediate along the concerted [3 + 2] addition pathway on the singlet potential energy is favored kinetically and thermodynamically over its formation by a two-step process via the metallaoxetane by [2 + 2] addition. The activation barriers for the formation of the dioxylate and the product stabilities on the singlet PES for the ligands studied are found to follow the order: NPH3 < Cl(-) < CH3O(-) < Cp < O(-) < CH3. On the doublet PES, the activation barriers for the formation of the dioxylate intermediate for the ligands are found to follow the order: CH3O(-) < Cl(-) < Cp < CH3 while the order of product stabilities is: Cl(-) < CH3O(-) < Cp < CH3. The order of dioxylate product stabilities on the triplet surface for the ligands studied is: Cl(-) < CH3O(-) < Cp < CH3 < NPH3 < O(-) and the order on the quartet surface is O(-) < Cp < CH3 < NPH3 < Cl(-) < CH3O(-). The re-arrangement of the metallaoxetane intermediate to the dioxylate is not a feasible reaction for all the ligands studied. Of the group VII B metal oxo complexes studied, MnO4(-) and MnO3(OCH3) appear to be the best catalysts for the exclusive formation of the dioxylate intermediate, MnO3(OCH3) being better so on both kinetic and thermodynamic grounds. The best epoxidation catalyst for the Mn complexes is MnO3Cl; the formation of the epoxide precursor will not result from the reaction of LMnO3 (L = O(-), Cp) with ethylene on any of the surfaces studied. The trends observed for the oxidation reactions of the Mn complexes with ethylene compare closely with those reported by us for the ReO3L and TcO3L (L = O(-), Cl, CH3, OCH3, Cp, NPH3) complexes, but there is far greater similarity between the Re and Tc complexes than between Mn and either of the other two. There does not appear to be any singlet-triplet or doublet-quartet spin-crossover in any of the pathways studied.

Zeolites A was synthesized from alternate sources such as filtrate from synthesized zeolite LSX and aluminate solution extracted from bauxite which produced a very good yield. The synthesized zeolite type was characterized by X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX). The synthesized product showed a high degree of crystallinity from the XRD results. When applied to a spent lubricating oil, the efficiency in removing the heavy metals was: 23.4% Fe, 96.8% Zn, 19.0% Cu, and 12.0% Cr. The saturates in the regenerated oil were 80% carbon, 4% residue, and 16% aromatics as compared to that of a commercial virgin oil that contained 84% saturates, 3% carbon residue, and 13% aromatics. This indicated that the spent oil can be reused.

Insight into the detailed mechanism of the Sabatier reaction on iron is essential for the design of cheap, environmentally benign, efficient and selective catalytic surfaces for CO 2 reduction. Earlier attempts to unravel the mechanism of CO 2 reduction on pure metals including inexpensive metals focused on Ni and Cu; however, the detailed mechanism of CO 2 reduction on iron is not yet known. We have, thus, explored with spin-polarized density functional theory calculations the relative stabilities of intermediates and kinetic barriers associated with methanation of CO 2 via the CO and non-CO pathways on the Fe (111) surface. Through the non-CO (formate) pathway, a dihydride CO 2 species (H 2 CO 2), which decomposes to aldehyde (CHO), is further hydrogenated into methoxy, methanol and then methane. Through the CO pathway, it is observed that the CO species formed from dihydroxycarbene is not favorably decomposed into carbide (both thermodynamically and kinetically challenging) but CO undergoes associative hydrogenation to form CH 2 OH which decomposes into CH 2 , leading to methane formation. Our results show that the transformation of CO 2 to methane proceeds via the CO pathway, since the barriers leading to alkoxy transformation into methane are high via the non-CO pathway. Methanol formation is more favored via the non-CO pathway. Iron (111) shows selectivity towards CO methanation over CO 2 methanation due to differences in the rate-determining steps, i.e., 91.6 kJ mol −1 and 146.2 kJ mol −1 , respectively. Keywords Spin-polarized DFT-GGA • CO 2 methanation • CO methanation • Methanol formation • Reaction mechanism CO 2 + 4 H 2 → CH 4 + 2 H 2 O ΔH 298K = −252.9 kJ mol −1 .