Metal Borate Research Articles

In1–xGaxBO3 (0 ≤ x ≤ 0.5) – Solvothermal Synthesis, Morphology, and Performance in Photocatalytic Water Reduction

Partial solid solutions of In1–xGaxBO3 (0 ≤ x ≤ 0.5) were synthesized by the solvothermal method, and they were characterized by powder X‐ray diffraction, scanning and transmission electron microscopy, UV/Vis absorption spectroscopy, and N2 adsorption–desorption, in order to identify the phase purity and micromorphology. Nanocrystallites of InBO3 exhibit a particular anisotropic growth along the [110] direction, forming spindlelike morphology (with a diameter of ca. 20 nm and a length of ca. 200 nm). These nanocrystallites further aggregate into microspheres. With Ga3+ substitution, the anisotropic growth was depressed; the nanocrystallites thus exhibited a typical rodlike morphology. Metal borates are well‐known optical materials; however, their photocatalytic properties have been rarely studied. Here, post‐annealing under O2 flow at 350 °C improved the photocatalytic H2 evolution rate of InBO3 from 18.2(6) to 29.5(8) µmol h–1 g–1. A loading of Pt, RuOx, or NiOx as cocatalyst resulted in further enhancement of the H2 evolution rate, with an optimal value of 56.1(5) µmol h–1 g–1 under UV light.

Thermodynamic properties of two microporous materials for Na2[M2B12O21] (M = Co2+, Cu2+)

Two transition metal borates with microporous structures for Na2Co2B12O21 and Na2Cu2B12O21 have been synthesized and characterized by XRD, FT-IR, and elemental analysis. The molar enthalpies of solution of Na2Co2B12O21(s) and Na2Cu2B12O21(s) in 1moldm−3 HCl(aq) were measured by microcalorimeter at T=298.15K, respectively. The molar enthalpies of solution of CoCl2·6H2O(s) and CuCl2·2H2O(s) in the mixture solvent of 2.00cm3 of 1moldm−3 HCl(aq) in which 5.30mg of H3BO3 and 0.84mg of NaCl being added were also measured, respectively. With the incorporation of the previously determined enthalpy of solution of H3BO3(s) in 1moldm−3 HCl(aq), together with the standard molar enthalpies of formation for CoCl2·6H2O(s)/CuCl2·2H2O(s), NaCl(s), H3BO3(s), HCl(aq) and H2O(l), the standard molar enthalpies of formation of – (9072.4±9.7)kJmol−1 for Na2Co2B12O21(s) and – (8887.5±9.7)kJmol−1 for Na2Cu2B12O21(s) at T=298.15K were obtained on the basis of the appropriate thermochemical cycles. It is obvious that Na2Co2B12O21(s) is more thermal stable than that of Na2Cu2B12O21(s).

Intrinsic photocatalytic water reduction over PbGaBO4 comprising edge-sharing GaO6 chains

Metal borates are well-known optical materials while their semiconducting behavior, i.e. photocatalytic property, was less studied. Inspired by the recent publications on gallium borates with good photocatalytic performances, we investigated photocatalytic water reduction activity of another gallium borate, PbGaBO4, comprising edge-sharing GaO6-chains. Both conventional and solution assisted solid state reaction methods were employed for the preparation. Phase purity and the crystallinity of both samples were identified by powder X-ray diffraction and scanning electron microscopy. The UV–Vis reflectance spectra suggested the wide bandgap characteristic (4.10 eV) and theoretical calculations pointed out that the 6s and 5p orbitals of Pb2+ contribute to both the bottom of CB and the top of VB. However the ionic bonding of PbO in PbGaBO4 led to a slight hydrolysis during the photocatalysis process, which can be suppressed by loading cocatalysts of Pt and RuOx. In addition, such a surficial modification significantly improved the photocatalytic water reduction ability, with an optimal H2 evolution rate of 41.9(9) μmol/h/g under UV-light irradiation.

Thermochemical properties for a series of transition metal borates of M[B12O14(OH)10] (MII = Mn, Zn, Fe, Co, Ni)

A pure zinc borate, Zn[B12O14(OH)10], has been synthesized and characterized by XRD, FT-IR, simultaneous TG-DTA techniques, and chemical analysis. The molar enthalpy of solution of Zn[B12O14(OH)10] (s) in 1mol·dm−3 HCl(aq) was measured by microcalorimeter at T=298.15K. The molar enthalpy of solution of ZnO(s) in the mixture solvent of 2.00cm3 of 1mol·dm−3 HCl(aq) and calculated amount of H3BO3 was also measured. With the incorporation of the previously determined enthalpy of solution of H3BO3(s) in 1mol·dm−3 HCl(aq), together with the use of the standard molar enthalpies of formation for ZnO(s), H3BO3(s), and H2O(l), the standard molar enthalpy of formation of −(9646.6±9.6)kJ·mol−1 at T=298.15K was obtained on the basis of an appropriate thermochemical cycle. In addition, the molar enthalpy of formation of −9492.7kJ·mol−1 for [B12O14(OH)10]2− has also been estimated by a group contribution method, which has been used to predict the ΔfHmθ of a series of transition metal borates of M[B12O14(OH)10] (MII=Mn,Zn,Fe,Co,Ni). These estimated data have been used to further compare the stability of this series of transition metal borates.

A new acentric borate of K2Ba[B4O5(OH)4]2·10H2O: synthesis, structure and nonlinear optical property

A new acentric mixed metal borate of composition K2Ba[B4O5(OH)4]2·10H2O, has been successfully obtained by slow evaporation solution method. The compound crystallizes in the Orthorhombic space group Pna21 (No.33) with a = 16.8668(7) Å, b = 13.0903(5) Å, c = 11.5529(5) Å and Z = 4. [B4O5(OH)4]2− clusters serve as fundamental building unit linking with BaO8, K1O6, K2O7 by common O atoms to form three-dimensional layer structure. The second harmonic generation measurements in the powder samples reveal that the compound exhibits approximately 0.5 times that of KH2PO4 (KDP) and phase matching.

Solvothermal Synthesis and Structure of Two New Borates Containing [B7O9(OH)5]2− and [B12O18(OH)6]6− Clusters

Two new metal borates, K[B7O9(OH)5]·Hen (1, en = enthylenediamine) and Na2Cs4Ba2[B12O18(OH)6]·4(OH) (2) have been synthesized under solvothermal conditions. Their structures were determined by the single crystal X-ray diffraction and were further characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis and powder X-ray diffraction, respectively. 1 crystallizes in the triclinic system, P-1 space group, a = 7.7152(6), b = 8.4057(6), c = 12.1319(10) A, α = 92.505(6), β = 98.944(7), γ = 103.825(6)°, Z = 2. 2 crystallizes in the orthorhombic system, Pmn21 space group, a = 12.6972(6) A, b = 13.7037(6) A, c = 9.4968(5) A, Z = 2. Compound 1 consists of isolated [B7O9(OH)5]2− clusters which are held together through H-bonding interactions and K atoms to form a 3-D supramolecular framework. For 2, bowl-like isolated [B12O18(OH)6]6− clusters were linked together to form a 3-D framework by different metal ions and H-bond system.

Two New Crystals in Li(m)Cs(n)B(m+n)O2(m+n) (m + n = 5, 7; m > n) Series: Noncentrosymmetric Li5Cs2B7O14 and Centrosymmetric Li4CsB5O10.

With the introduction of an alkali metal into the B-O framework, two new alkali metal borate crystals, Li5Cs2B7O14 and Li4CsB5O10, have been obtained for the first time. Both compounds obey a general formula of Li(m)Cs(n)B(m+n)O2(m+n) (m + n = 5, 7; m > n). The two crystals have different three-dimensional (3D) framework structures composed by LiOn (n = 4, 5), CsO10, BO3, and BO4 units. Li5Cs2B7O14 crystallizes into the polar and noncentrosymmetric space group Ama2, while Li4CsB5O10 belongs to the nonpolar and centrosymmetric space group P21/c. Detailed structure comparison analysis indicates that the different arrangements of the anionic groups in Li(m)Cs(7-m)B7O14 (m = 4, 5) and Li(m)Cs(5-m)B5O10 (m = 3, 4) may arise from the cation size effects, bond-valence requirements, and differences of coordination environment. In addition, in order to get better understandings of electronic structures and linear optical properties, we also carried out first-principle theoretical studies.

Defect-Tolerant Diffusion Channels for Mg2+ Ions in Ribbon-Type Borates: Structural Insights into Potential Battery Cathodes MgVBO4 and MgxFe2–xB2O5

The reversible room temperature intercalation of Mg2+ ions is difficult to achieve but may offer substantial advantages in the design of next-generation batteries if this electrochemical process can be successfully realized. Two types of quadruple ribbon-type transition metal borates (MgxFe2–xB2O5 and MgVBO4) with high theoretical capacities (186 and 360 mAh/g) have been synthesized and structurally characterized through the combined Rietveld refinement of synchrotron and time-of-flight neutron diffraction data. Neither MgVBO4 nor MgxFe2–xB2O5 can be chemically oxidized at room temperature, though Mg can be dynamically removed from the latter phase at elevated temperatures (approximately 200–500 °C). It is found that Mg diffusion in the MgxFe2–xB2O5 structure is more facile for the inner two octahedral sites than for the two outer octahedral sites in the ribbons, a result supported by both the refined site occupancies after Mg removal and bond valence sum difference map calculations of diffusion paths in ...

Ba2B6O11, a Member of the BaO‐B2O3 Family, Featuring a Layer Framework

AbstractBa2B6O11, a new member of the BaO‐B2O3 family, has been found and features a layered structure. The single‐crystal X‐ray structural analysis revealed that Ba2B6O11 crystallizes in the monoclinic space group P21/c. The parameters of the monoclinic unit cell are a = 9.115(1), b = 7.773(1), c = 12.696(2) Å, β = 100.325(9)°, and Z = 4. The new centrosymmetric alkaline earth metal borate, Ba2B6O11, is characterized by a 2D B–O framework composed of the basic building block (B6O14) with the Ba2+ cations filling the channels formed by the (B6O14) units or located between the (B6O10)∞ layers. Ba2B6O11 has a short cut‐off edge of 240 nm. Based on a theoretical calculation, it has been proven that Ba2B6O11 has a birefringence of 0.04 and a relatively large indirect band gap of 4.94 eV, which is close to the experimental value of 5.17 eV. Its structure is discussed in terms of the B–O framework and dimensional reduction formalism together with the other structures reported in the BaO‐B2O3 phase diagram.

Lithium metal borate (LiMBO3) family of insertion materials for Li-ion batteries: a sneak peak

Rechargeable lithium-ion battery remains the leading electrochemical energy-storage device, albeit demanding steady effort of design and development of superior cathode materials. Polyanionic framework compounds are widely explored in search for such cathode contenders. Here, lithium metal borate (LiMBO3) forms a unique class of insertion materials having the lowest weight polyanion (i. e., BO33-), thus offering the highest possible theoretical capacity (ca. 220 mAh/g). Since the first report in 2001, LiMBO3 has rather slow progress in comparison to other polyanionic cathode systems based on PO4, SO4, and SiO4. The current review gives a sneak peak to the progress on LiMBO3 cathode systems in the last 15 years highlighting their salient features and impediments in cathode implementation. The synthesis and structural aspects of borate family are described along with the critical analysis of the electrochemical performance of borate family of insertion materials.

Antiquenching effect of modifying cations on samarium clustering: Physical, structural and luminescent behavior of heavy metal borate glass systems

In this paper an attempt has been made to correlate the structural modifications and luminescence efficiencies by changing the environment of the glass network by modifying oxides. Sm3+ doped lead borate (SPB) and lead cadmium alumino borate (SCPB) glasses have been fabricated by melt quench technique at high temperature. The glass samples are characterized by XRD, FTIR, optical absorptions, fluorescence and density measurements. The effect of Sm3+ ion and glass host interaction on the emission spectra has been discussed in the view of the ionicity and covalency of hosts. The ratio of the intensities of electric to magnetic dipole emissions are calculated by varying both the concentration of the Sm3+ ion and the composition of the glass matrix. The XRD profile of all the glasses confirms their amorphous nature and FTIR spectrum shows the presence of BO3 and BO4 groups. These glasses have shown strong absorption bands in the visible (VIS and NIR) region and emit strong orange red wavelengths when excited by ultraviolet light. The concentration quenching has been noticed and ascribed to energy transfer through cross-relaxation between Sm3+ ions. Shifting of UV absorption edge towards longer wavelength with addition of Sm2O3 concentration has been observed. Incorporation of Al2O3 and CdO in 2nd glass system is responsible for strong effect on luminescence of the present glass system. Based on these results, an attempt has been made to throw some light on the relationship between the structural modifications and luminescence efficiencies in two different glass hosts as a laser active medium in the visible region. Moreover the optical basicity values were theoretically determined along with covalent behavior of two glass systems.

Two New Mixed Metal Borates Made of Mg(B6O7(OH)6)2 and B8O14(OH)4 Cluster Units

Two new mixed metal borates, Li2[Mg(B6O7(OH)6)2]·2H2O (1) and Li4Ca2[B8O12(OH)4]2·3H2O (2) have been made under solvothermal conditions and characterized by FT-IR spectroscopy, powder X-ray diffraction, single crystal X-ray diffraction and thermogravimetric analysis, respectively. Crystal data for 1: triclinic, \({P_{\bar 1}}\), a = 6.9415(4) A, b = 9.1626(5) A, c = 9.4540(6) A, α = 71.697(6)o, β = 88.431(5)o, γ = 68.409(5)o, Z = 1. Crystal data for 2: monoclinic, C2/c, a = 19.8507(5) A, b = 6.7560(2) A, c = 20.0454(5) A, β = 93.985(2)o, Z = 4. In structure 1, the structural building unit (SBU), sandwich type [Mg(B6O7(OH)6)2]2−, connects adjacent six same ones to form a 2-D layer via Li-based polyhedra in the bc plane and further link by hydrogen bonding to form 3-D supramolecular network. In the structure 2, the SBUs, [B8O14(OH)4]8−, link together to produce a 2-D layer with 13-membered ring (MR) windows along the bc-plane. Such layers are further linked by Li-based polyhedra to form a 3-D framework.

Structural and optical properties of LiKB4O7 single crystals grown by Czochralski technique

One of the alkali metal borates, lithium potassium borate (LiKB4O7) single crystal, was grown following two different micro step pulling movements employing the modified crystal puller. The influence of two different micro step pulling movements on the crystalline nature, optical properties and micro morphology of the grown LiKB4O7 crystal was investigated by high resolution X-ray diffraction (HRXRD) analysis and birefringence interferometry and chemical etching techniques, respectively. HRXRD studies revealed that the crystalline perfection of the grown crystals is reasonably good. Interferometric images showed that the crystal grown under higher micro step pulling movement has very less number of scattering centers. The etching studies revealed that the crystal grown under higher micro steps pulling movement contains relatively low level dislocation density.

A novel lead borate of NaPb4(H2O)(B5O9)2·BO3 with nonlinear optical property

A new mixed metal borate, NaPb4(H2O)(B5O9)2·BO3, with an acentric structure has been successfully made under hydrothermal conditions and structurally characterized by IR spectroscopy, powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA) and single-crystal X-ray diffraction, respectively. The structural analysis shows that 1 crystallizes in the orthorhombic space group Pnn2 (No. 34) with a=11.3724(5) Å, b=11.4455(4) Å, c=6.5578(2) Å and Z=2. In the structure 1, the structural building unit, B5O12 cluster, connects adjacent six same ones to form a 3-D oxoboron framework with 8-membered ring (MR) and 10-MR channels along the c-axis. The Pb atoms and coordinated water molecules are located in the 8-MR channels, while the 10-MR channels were occupied by the chains built by Na atoms and the BO3 groups. Second-harmonic generation (SHG) measurements on the powder samples reveal that 1 exhibits SHG efficiency approximately 2 times that of KH2PO4 (KDP). Also it has a UV cutoff edge below 220nm.

ChemInform Abstract: Nanomaterials via Solution Combustion Synthesis: A Step Nearer to Controllability

AbstractReview: 117 refs.

Synthesis of boron nitride nanostructures from borates of alkali and alkaline earth metals

Boron nitride nanostructures (nanotubes, graphene-like petals, and columnar porous flakes) grew in reactions of alkali and alkaline earth borates with ammonia.

Na3B4O7X (X = Cl, Br): two new borate halides with a 1D Na-X (X = Cl, Br) chain formed by the face-sharing XNa6octahedra

Two new borate halides consist of a B4O9framework and a [Na3Br] chain which have not been found in other alkali metal borate halides.

Synthesis, crystal structure and properties of a new barium calcium borate, Ba2Ca2(B2O5)2

A new mixed alkaline earth metal borate, Ba2Ca2(B2O5)2, has been synthesized by standard solid-state reaction method and the crystal structure has been determined by the single crystal X-ray diffraction method. It crystallizes in the monoclinic system, space group P21/c (No. 14) with a = 6.568(2) Å, b = 20.545(7) Å, c = 8.201(2) Å, β = 117.00(2) °, and Z = 4. The structure contains an infinite three-dimensional (3D) matrix that is built up of BaOn (n = 7, 9) polyhedra, CaO6 octahedra and isolated B2O5 groups. Specifically, the configuration and arrangement of the B2O5 groups are discussed comparing with those in other two alkaline earth metal borates, MgSrB2O5 and Mg3Ca3(B2O5)3. Thermal stability measurements reveal that Ba2Ca2(B2O5)2 melts incongruently at 1015 °C. Optical properties of Ba2Ca2(B2O5)2 were investigated and the first-principle theoretical calculations were performed to understand the electronic structure.

Two-coordinate Dialkylsilylene–Coinage Metal Complexes

Abstract Two-coordinate dialkylsilylene–coinage metal complexes 3+·TPFPB− (Cu) and 4+·TPFPB− (Ag) were synthesized as the first dialkylsilylene–copper complex and the first silylene–silver complex, respectively, by the reaction of dialkylsilylene 1 with the corresponding metal borate. X-ray analysis showed that both the complexes adopted a linear structure with two perpendicular dialkylsilylene units. Theoretical study indicated that weak π back-donation of the copper and silver complexes compared to that of the corresponding isoelectronic neutral palladium complex would be due to low-lying d orbitals of Cu+ and Ag+ centers and responsible for the linear structures.

Enhanced Electrochemical Performance of Monoclinic LiMnBO3-Based Li Storage Material Via Partial Substitution

We developed a new electrochemically active Li storage material based on a polyanionic framework. By replacing a portion of Mn with Fe and Mg in monoclinic lithium manganese borate (LiMnBO3), a phase-pure LiMn0.5Fe0.4Mg0.1BO3 was successfully synthesized. A C/50-rate galvanostatic discharge delivered a near theoretical capacity of 201 mAh g-1 at room temperature with much improved rate capability, 120 mAh g-1 at a 1C discharge, compared to other borate chemistries. We explained this superior Li storage activity in relation to the topological effect of substitution, which leads to facile Li diffusion and stabilizes the structure. Combining with the inherent stability of the borate group against oxygen evolution, we believe that the enhanced electrochemical properties achieved in this study makes the LiMn0.5Fe0.4Mg0.1BO3 compound a strong contender as a new cathode material for Li-ion batteries and will bring more attention to the lithium transition metal borate chemistry.