Electronic Structure of Tantalum Oxynitride Perovskite Photocatalysts. -The absolute conduction and valence band energy levels of MTaO2N (M: Ca, Sr, Ba) and PrTaON2, which are promising candidates for photocatalytic splitting of water under visible light irradiation, are determined by a combination of XPS, Kelvin probe force microscopy, UV/VIS spectroscopy, and depth-resolved cathodoluminescence spectroscopy. All four compounds have conduction band edges that lie above the reduction potential for water and valence band edges which lie near the oxidation potential of water. The position of the conduction band edge is closely linked to the Ta-O/N-Ta bond angles, whereas the position of the valence band edge is more sensitive to the oxygen--to-nitrogen ratio. -(BALAZ*, S.; PORTER, S. H.; WOODWARD, P. M.; BRILLSON, L. J.; Chem. Mater. 25 (2013) 16, 3337-3343,

Pristine and boron-doped anatase TiO2 were prepared via a facile sol-gel method and the hydrothermal method for application as anode materials in sodium-ion batteries (SIBs). The sol-gel method leads to agglomerated TiO2, whereas the hydrothermal method is conducive to the formation of highly crystalline and discrete nanoparticles. The structure, morphology, and electrochemical properties were studied. The crystal size of TiO2 with boron doping is smaller than that of the nondoped crystals, which indicates that the addition of boron can inhibit the crystal growth. The electrochemical measurements demonstrated that the reversible capacity of the B-doped TiO2 is higher than that for the pristine sample. B-doping also effectively enhances the rate performance. The capacity of the B-doped TiO2 could reach 150 mAh/g at the high current rate of 2C and the capacity decay is only about 8 mAh/g over 400 cycles. The remarkable performance could be attributed to the lattice expansion resulting from B doping and the shortened Li(+) diffusion distance due to the nanosize. These results indicate that B-doped TiO2 can be a good candidate for SIBs.

Compatible with various common solvents, a new electrolyte salt NaDFOB has been studied, which enables excellent reversible capacity and high rate capability when used in Na/Na0.44MnO2 half cells.

Symmetries and model structures are given for ABN2O (and ABNO2) perovskites that possess long-range ordering of anions in combination with a 0 a 0 c –, a – b 0 a –, and a – b + a – octahedral tilting. The stabilities of competing structures have been evaluated using density functional theory (DFT) calculations, which show that cis-ordered models are more stable than competing trans-ordered polymorphs. To test the validity of these predictions, the perovskite nitride oxides LaTaN2O, CeTaN2O, and PrTaN2O have been synthesized and characterized using neutron powder diffraction. CeTaN2O and PrTaN2O crystallize with orthorhombic Pnma symmetry (Ce: a = 5.69666(8), b = 8.03272(9), and c = 5.70893(7) Å; Pr: a = 5.6868(1), b = 8.0153(1), and c = 5.68057(8) Å) as a result of a – b + a – tilting of the octahedra. The structure of LaTaN2O is re-examined and found to possess orthorhombic Imma symmetry (a = 5.7093(1), b = 8.0591(2), and c = 5.7386(2) Å) as a result of a – b 0 a – tilting. No evidence for long-range anion order is found in any of the three compounds. Optical band gaps for these compounds are measured to be 2.0 eV (LaTaN2O), 1.9 eV (CeTaN2O), and 2.0 eV (PrTaN2O). These values are 0.6–0.7 eV smaller than CaTaNO2 where the Ta-centered octahedra tilt by a similar amount. As the nitrogen content increases, there is an increase in the overlap of the anion 2p orbitals, which increases the energy of the valence band maximum and narrows the band gap.

Reducing the dimensionality of inorganic lattices allows for the creation of new materials that have unique optoelectronic properties. We demonstrate that a layered metal chalcogenide lattice, TiS(2), can form a dimensionally reduced crystalline one-dimensional hybrid organic/inorganic TiS(2)(ethylenediamine) framework when synthesized from molecular precursors in solution. This solid has strong absorption above 1.70 eV and pronounced emission in the near-IR regime. The energy dependence of the absorption, the near-IR photoluminescence, and electronic band structure calculations confirm that TiS(2)(ethylenediamine) has a direct band gap.