Exploration of the oxygen reduction reaction activity of four transition metal borates: synthesis, structure and characterization

Four new transition metal borates, [Co(1-MI)₂]·B₅O₇(OH)₃ (1, 1-MI = 1-methylimidazole), Co₂(PZ)₈(SO₄)₂·2H₃BO₃ (2, PZ = pyrazole), K₇{(BO₃)Co[B₁₂O₁₈(OH)₆]}·H₂O (3) and K₂{[Ni(PY)₂]₂·[(C₄H₂O₆)₂B]}₂ (4, PY = pyridine), have been successfully synthesized by a mild method. Their structures were determined by X-ray single crystal diffraction. These compounds were further characterized by FTIR, PXRD and UV-vis-NIR. It is worth noting that the catalytic properties of catalysts based on these four borates were explored, and that organically templated borate 1- and 2-based catalysts showed better ORR catalytic performance compared to 3- and 4-based catalysts. This may be caused by the supramolecular skeletons of 1 and 2 providing sufficient space and porosity.

Sensitization of Mn2+ luminescence via efficient energy transfer to suit the application of high color rendering WLEDs

Developing novel luminescent materials with ideal properties is an endless project, urged by growing requirements of advances in energy saving, healthy lighting and environmental friendliness. Herein, a series of ScCaOBO3:Ce3+,Mn2+...

Site-occupancy scheme in disordered Ca3RE2(BO3)4: a dependence on rare-earth (RE) ionic radius

The structures of polycrystalline Ca₃RE₂(BO₃)₄ (RE = La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Y; space group Pnma) orthoborates were determined using powder X-ray diffraction. Trends in the unit-cell dimensions and yet unreported trends in other structural properties (interatomic distances and the fractional occupation of three Ca/RE sites) for these compounds are demonstrated as a function of RE ionic radius. The unit-cell volume and a unit-cell parameter present a linear dependence, while the b and c unit-cell parameters change in a nonlinear manner. For the whole series, the RE atoms are present at all three cationic sites (labelled as M1, M2 and M3), but the fractional occupancies depend on the RE ionic radius. The small rare-earth atoms tend to enter mainly the M3 site; for the larger rare earths, the occupancy of this site decreases sharply. The occupancy of the M1 site by RE atoms is around 0.5 and tends to increase with increasing RE ionic radius. The M2 site is the least preferentially occupied by RE ions, but the occupancy discernibly increases with rising radius as well. These findings are assembled with properties of isostructural strontium and barium borates, allowing prediction of occupancy schemes for not yet investigated compounds from the A₃RE₂(BO₃)₄ (A = Ca, Ba, Sr).

A novel Dy3+-activated single-phase white light-emitting phosphor for solid-state lighting

The doping of Dy3+ in the SCB host is capable of producing blue, yellow and red emissions, and therefore, SCB:Dy3+ can serve as a single-phase white-light-emitting phosphor for solid state lighting.

Synthesis and characterization of three new rare-earth orthoborates: Ba2MgY2(BO3)4, Ba2CdY2(BO3)4, and Ba2CdSc(BO3)3

Three rare-earth orthoborates Ba₂MgY₂(BO₃)₄, Ba₂CdY₂(BO₃)₄, and Ba₂CdSc(BO₃)₃ were synthesized via a high-temperature solution method and their structures were determined by single crystal X-ray diffraction for the first time.

Scandium Molybdate Microstructures with Tunable Phase and Morphology: Microwave Synthesis, Theoretical Calculations, and Photoluminescence Properties

In this paper, scandium molybdate microstructures have been prepared from solution via a microwave heating method. By controlling the experimental parameters such as molar ratio of reagent and reaction time, scandium molybdates with tunable phase and diverse morphologies including snowflakes, microflowers, microsheets, and branched spindles were obtained. The density of states and surface energies of Sc₂Mo₃O₁₂ were primarily studied from first-principles calculations. An indirect band gap of 3.56 eV was observed for crystalline Sc₂Mo₃O₁₂, and the surface energies of various facets were determined to be 0.27-0.91 J/m². The influence of n(Sc³⁺): n(Mo₇O₂₄^6-) (short for Sc/Mo) molar ratio was systematically investigated and well-characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and UV-vis absorption spectroscopy (UV-vis). Results indicate that the Sc/Mo molar ratio has a great effect on the phase and morphology. Diffuse reflection spectra (DRS) revealed the E_gap can be readily tuned from 3.69 to 4.16 eV, which is in accordance with the theoretical result. The photoluminescence (PL) properties of Eu³⁺-doped Sc₂Mo₃O₁₂ were discussed. This facile synthesis strategy could be extended to the synthesis of other molybdates.

Three Cadmium Tartratoborates with Good Second Harmonic Generation (SHG) or Luminescence Performances

Three new cadmium(II) tartratoborates, namely, Cd₅[(C₄H₂O₆)₂B]₂(H₂O)₈·3H₂O (1), K₂Cd₄[(C₄H₂O₆)₂B]₂(H₂O)₂ (2), and Li_0.92K_1.08Cd_1.5[(C₄H₂O₆)₂B](H₂O)₂ (3), have been successfully synthesized by the hydrothermal method. Compounds 1-3 belong to centric C2/ c, acentric Pc, and the polar C2, respectively. Through based on the same hybrid borate-tartrate [(C₄H₂O₆)₂B]^5- anions, they exhibit different structures. The [(C₄H₂O₆)₂B]^5- anion is composed of two tartrate anions and a B(OH)₄^- unit. Compound 1 features a novel 3D network formed by 2D {Cd₃[(C₄H₂O₆)₂B]₂(H₂O)₂}^4- anionic layers and [Cd₂O₁₀] dimers, forming tunnels of large 14-MRs which are filled by the non-coordination water molecules. Compound 2 has a characteristic 3D network based on {Cd₂[(C₄H₂O₆)₂B]}^- units interlinked via carboxylate groups, forming tunnels of 11-MRs, half of which stuffed with the K⁺ ions. Compound 3 features 2D {Cd₄[(C₄H₂O₆)₄B]}³⁺ layers which are separated by K/Li ions. Luminescent studies suggest that they emit blue light. Compounds 2 and 3 display phase-matchable second harmonic generation signs of about 3.2× and 1.5× KH₂PO₄, respectively.

Ba3B10O17Br2: a new barium borate halide with B–O layered structure

A new barium borate halide, Ba₃B₁₀O₁₇Br₂, has been obtained, and is the first barium borate halide with a B–O layered structure.