Mesoporous SnO2-MoO3 catalyst for diesel oxidative desulfurization: Impact of the SnO2/MoO3 ratio on catalytic efficiency.

Vehicular SOx emissions have a huge detrimental impact on public health, catalytic converters, and the environment. Developing strategies to remove sulfur from diesel and thus safeguard the above is imperative. A series of SnO2-MoO3 mixed oxides and mono oxides MoO3 and SnO2 were prepared by soft template method, calcined at 450 °C and successfully tested in model diesel oxidative desulfurisation (ODS). The impact of the SnO2/MoO3 mole ratio (hereinafter denoted as Sn/Mo) on catalytic efficiency was investigated, among other catalytic parameters. The obtained samples were analyzed using X-ray diffraction (XRD), Raman spectrocscopy, scanning electron microscopy (SEM), N2-physisorption and titration method for acidic properties. The study demonstrates that mixing SnO2 and MoO3 improves acidic sites, crystallinity, and morphological properties of pure SnO2. The addition of MoO3 increased oxygen vacancies and the surface area of SnO2. High acidic site densities of 49.3, 47.4, and 46.7 mEqg-1 were observed for the catalysts with 2:1, 1:1, and 1:2 Sn/Mo mole ratio, respectively. The catalytic efficiency increased with an increase in Sn content with the highest catalytic efficiency of 99.8% for the dibenzothiophene (DBT) oxidation achieved in 30 min for Sn/Mo (2:1) catalyst compared to 92 and 70% for Sn/Mo 1:1 and 1:2 catalysts, respectively. The rate constant for the reaction was 0.057 min-1, which is eight times that of MoO3; 0.007 min-1 and three times that of SnO2; 0.017 min-1. The ODS mechanism utilizing the SnO2-MoO3 catalyst was proposed. The prepared SnO2-MoO3 catalyst demonstrated a high potential for industrial desulfurisation applications.

Gaseous complex hydrides NaMH4 and Na2MH5 (M = B, Al) as hydrogen storage materials: a quantum chemical study.

Metal hydrides are feasible for energy storage applications as they are able to decompose with hydrogen gas release. In this work, gaseous complex sodium hydrides, NaMH4 and Na2MH5 (M = B or Al), have been investigated using DFT/B3P86 and MP2 methods with 6-311++G(d,p) basis set; the optimized geometry, vibrational spectra and thermodynamic (TD) properties have been determined. Based on TD approach, a stability of the hydrides to different dissociation channels is analysed; the enthalpies of formation ∆fH°(0) of gaseous species have been obtained: - 1 ± 17 kJ mol-1 (NaBH4), 91 ± 14 kJ mol-1 (NaAlH4), - 13 ± 16 kJ mol-1 (Na2BH5), and 71 ± 16 kJ mol-1 (Na2AlH5). The complex hydrides are confirmed to produce gaseous products with hydrogen gas release at elevated temperature, whereas heterophase reactions, with NaH and B/Al products in condensed state, are predicted to occur spontaneously at lower temperature. Graphical abstract.

Effects of heteroatoms in π-conjugated linkers on the optical and electronic properties of modified triphenylamine based dyes: towards DSSCs' applications.

Optoelectronic properties of triphenylamine dyes arising from the embedded five-membered π-linkers C4H4X (X = O, NH, S, Se, Te) and varying anchoring groups, cyanoacrylic acid and hydantoin, in D-π-π-A model are examined. The reported properties for both, isolated dyes and dye@TiO2 complexes, are realized through density functional theory (DFT) and time-dependent DFT. The study reveals that chalcogen doping (X = S, Se, Te) enhances absorption and fluorescent emission spectra in the visible and NIR regions. The adsorption of the dyes on the TiO2 cluster has been simulated. Alteration of the UV-Vis spectra and electron density redistribution for the complexes from individual dyes are examined and analyzed. The binding energies relate to the nature of the heteroatoms X; the complexes dye@TiO2 with heavier heteroatoms Se and Te demonstrate stronger binding. Graphical abstract.

Lawsone isomers, lawsone ether and bilawsone for dye-sensitized solar cells applications: DFT and UV-Vis studies.

Structural and optoelectronic properties of lawsone (L), lawsone ether (LE) and bilawsone (BL) were studied theoretically using the DFT and time-dependent DFT methods with hybrid functional B3LYP5 and 6-311G (2d,p) basis set. For the monomer lawsone molecule, isomerization reaction between two rotational isomers was analyzed based on a thermodynamic approach. The electronic spectra of the dyes molecules in a vacuum and solvents (DMSO and CH2Cl2) were computed. The maximum wavelengths were found at 355-408 nm for the LE and 350-448 nm for BL that indicated bands shift to visible range compared to L (340 nm). The UV-Vis spectra of the L and BL were measured experimentally in DMSO solution. For the BL, a broad and intensive band was observed in a visible region at 452 nm that apparently would favour sensitizing ability of the dye. The optoelectronic properties of the LE and BL showed them as more promising candidates for DSSCs applications compared to the individual lawsone dye.

Tuning optoelectronic properties of triphenylamine based dyes through variation of pi-conjugated units and anchoring groups: A DFT/TD-DFT investigation.

Dye-sensitized solar cells (DSSCs) have attracted widespread attention due to their unique features. In the present work, molecular engineered triphenylamine based dyes featuring donor-bridge-acceptor architecture have been considered and investigated for suitable properties for DSSCs applications. Hydantoin anchoring group has been introduced replacing the commonly used cyanoacrylic acid to improve the long-term stability of the device. Results on the effects of varied anchoring groups and pi-spacers have been interpreted from the viewpoint of DFT/TD-DFT calculations. Designed sensitizers exhibit suitable light-harvesting efficiencies, excited-state lifetimes, electron injection and regeneration abilities. Red-shifted electronic spectra are observed for three hydantoin dyes compared to others in the same family. Further analysis of chemical descriptors and observation from full-electron donor-acceptor map reveal that the three dyes among nine are potential materials with promising properties towards improving DSSCs performance.