Insoluble Fe(VI) compounds: effects on the super-iron battery

Cathodes composed of Fe(VI) salts are capable of three-electron reduction, and are useful for energetic super-iron batteries. This study investigates the solubility of BaFeO₄ and K₂FeO₄ Fe(VI) salts. Electrolytes are determined in which Fe(VI) has a low aqueous or non-aqueous solubility, or is insoluble. Insoluble Fe(VI) salts have the duel benefits of preventing Fe(VI) solution-phase (i) decomposition and (ii) diffusion to the anode; thereby preventing super-iron battery self-discharge. BaFeO₄ is insoluble in water, and has a solubility of less than 2×10⁻⁴ M in 5 M KOH containing Ba(OH)₂. A BaFeO₄ super-iron battery has a high discharge efficiency when containing an electrolyte of either 12 M KOH, or 6 M KOH saturated in Ba(OH)₂. Fe(VI) cathodes in non-aqueous media may be useful in providing a high-capacity Li or Li-ion super-iron battery. We illustrate that Fe(VI) salts are insoluble and chemically unreactive with a range of organic electrolytes, and can be discharged as cathodes in non-aqueous electrolytes. In acetonitrile containing 1 M LiClO₄, the discharge of an Fe(VI) cathode is demonstrated to a capacity over 394 mAh g⁻¹ K₂FeO₄.     

SrFeO4: Synthesis,Fe(VI) characterization and the strontium super-iron battery

Cathodes comprised of Fe(VI) salts, and capable of three electron reduction, are useful for the formation of energetic super-iron batteries. This study presents a synthesis procedure for SrFeO₄ or strontium super-iron cathodic salts, and also introduces mixed salts containing barium and strontium cations, Sr_xBa_(1−x)FeO₄. The X-ray diffraction and first IR spectra of SrFeO₄ are presented, and compared to known spectra of K₂FeO₄ and BaFeO₄. The measured solubility of SrFeO₄ is low in concentrated KOH electrolytes (0.001 mM in 13.5 M KOH), of use for alkaline cathodic chemistry. AAA batteries were prepared and discharged with this new cathode, and exhibit high discharge energies, approaching, but lower than those previously observed for barium super-iron alkaline batteries. The discharge energy further approaches the barium cell when the mixed cathode salt is employed, particularly for x=0.25–0.5 in Sr_xBa_(1−x)FeO₄.     

Rapid chemical synthesis of four ferrate(VI) compounds

The preparation of four novel Fe(VI) salts, including PbFeO₄, ZnFeO₄, CdFeO₄ and HgFeO₄ is demonstrated. These Fe(VI) salts were synthesized from a solid phase reaction merely by grinding K₂FeO₄ with M (C₂H₃O₂)₂.nH₂O (M = Pb²⁺, Zn²⁺) or M (NO₃)₂.nH₂O (M = Cd²⁺, Hg²⁺) at room temperature. A rapid and efficient reaction occurred upon grinding the solid reactants to afford high yield ferrate(VI) salts which were characterized by XRD, EDS and FTIR techniques. All of the synthesized ferrates were rather stable and could be stored at room temperature for more than a month with no significant decomposition.     

Enhanced Fe(VI) cathode conductance and charge transfer: effects on the super-iron battery

Cathodes comprising Fe(VI) salts are capable of three-electron reduction, and are useful for the formation of energetic ‘super-iron’ batteries. Material additions to the Fe(VI) cathode can be used to enhance the conductance and the efficiency of charge transfer to the cathode, and control the characteristics of the electrochemical storage. Whereas several common carbons are ineffective as conductive matrices for Fe(VI) reduction, several others such as small particle (1 μm) graphite, compressed carbon black, and fluorinated polymer graphites support efficient Fe(VI) 3e⁻ reduction. Several inorganic salts also sustain Fe(VI) reduction, but at lower current densities. Titanates and other salts added to a K₂FeO₄ cathode improve the faradaic efficiency of Fe(VI) reduction at higher (∼3 mA cm⁻²) discharge current densities. Fluorinated polymer graphites provide an unusual additive to the Fe(VI) cathode mix, and at a low level (10 wt.%) addition can support efficient Fe(VI) reduction.     

Direct electrochemical preparation of solid Fe(VI) ferrate,and super-iron battery compounds

The electrochemical generation of Fe(VI) salts eliminates requirements for chemical oxidants and decreases the synthesis complexity. An alternate electrochemical synthesis from an iron anode in alkaline electrolyte is presented for the in situ direct synthesis of the solid Fe(VI) salts, such as BaFeO₄. A variety of electrolysis conditions including cell configuration, applied current density, temperature, synthesis duration, electrolyte composition and concentration, and the molar ratio between the reactants have been explored. In situ electrochemically synthesized BaFeO₄ exhibits similar valence, IR absorption spectrum and X-ray powder diffraction as the chemically synthesized material.     

Thermal decomposition of iron(VI) oxides, K2FeO4 and BaFeO4, in an inert atmosphere

The thermal decomposition of solid samples of iron(VI) oxides, K₂FeO₄·0.088 H₂O (1) and BaFeO₄·0.25H₂O (2) in inert atmosphere has been examined using simultaneous thermogravimetry and differential thermal analysis (TG/DTA), in combination with in situ analysis of the evolved gases by online coupled mass spectrometer (EGA-MS). The final decomposition products were characterized by ⁵⁷Fe Mössbauer spectroscopy. Water molecules were released first, followed by a distinct decomposition step with endothermic DTA peak of 1 and 2 at 273 and 248 °C, respectively, corresponding to the evolution of molecular oxygen as confirmed by EGA-MS. The released amounts of O₂ were determined as 0.42 and 0.52 mol pro formula of 1 and 2, respectively. The decomposition product of K₂FeO₄ at 250 °C was determined as Fe(III) species in the form of KFeO₂. Formation of an amorphous mixture of superoxide, peroxide, and oxide of potassium may be other products of the thermal conversion of iron(VI) oxide 1 to account for less than expected released oxygen. The thermogravimetric and Mössbauer data suggest that barium iron perovskite with the intermediate valence state of iron (between III and IV) was the product of thermal decomposition of iron(VI) oxide 2.     

Synthesis,structure, and thermal expansion of sodium zirconium arsenate phosphates

Sodium zirconium arsenate phosphates NaZr₂(AsO₄) _x (PO₄)_3?x were synthesized by precipitation technique and studied by X-ray diffraction and IR spectroscopy. In the series of NaZr₂(AsO₄) _x (PO₄)_3?x , continuous substitution solid solutions are formed (0 ≤ x ≤ 3) with the mineral kosnarite structure. The crystal structure of NaZr₂(AsO₄)_1.5(PO₄)_1.5 was refined by full-profile analysis: space group R \(\bar 3\) c, a = 8.9600(4)Å, c = 22.9770(9) Å, V = 1597.5(1) ų, R _wp = 4.55. The thermal expansion of the arsenate-phosphate NaZr₂(AsO₄)_1.5(PO₄)_1.5 and the arsenate NaZr₂(AsO₄)₃ was studied by thermal X-ray diffraction in the temperature range of 20–800°C. The average linear thermal expansion coefficients (α_av = 2.45 × 10^?6 and 3.91 × 10^?6 K^?1, respectively) indicate that these salts are medium expansion compounds.     

Synthesis,crystal structures,and catalytic oxidation of olefins of dioxomolybdenum(VI) complexes with aroylhydrazone ligands

Two Mo(VI) aroylhydrazone complexes, cis-[MoO₂(L¹)(CH₃OH)] (I) and cis-[MoO₂(L²)(CH₃OH)] (II), derived from 2-bromo-N'-(3,5-dibromo-2-hydroxybenzylidene)benzohydrazide (H₂L¹) and 2-bromo-N'-(2-hydroxy-4-methoxybenzylidene)benzohydrazide (H₂L²), respectively, are reported. The complexes were characterized by elemental analyses, infrared and electronic spectroscopy, and single crystal structure analysis (CIF files CCDC nos. 1443679 (I) and 1443678 (II)). The Mo atoms are coordinated by two cis terminal oxygen, ONO from the aroylhydrazone ligand, and methanol oxygen. Complex I crystallized as monoclinic space group P2₁/_c with unit cell dimensions a = 8.075(2), b = 13.905(1), c = 16.448(1) Å, β = 91.282(2)°, V = 1846.5(4) ų, Z = 4, R ₁ = 0.0859, wR ₂ = 0.2066. Complex II crystallized as triclinic space group P \(\overline 1 \), with unit cell dimensions a = 8.0824(6), b = 10.5919(8), c = 10.7697(8), α = 96.432(2)°, β = 97.438(2)°, γ = 103.119(2)°, V = 880.8(1) ų, Z = 2, R ₁ = 0.0271, wR ₂ = 0.0571. The complexes were tested as catalyst for the oxidation of olefins and showed effective activity.     

Conductive-matrix-mediated alkaline Fe(III/VI) charge transfer: three-electron storage, reversible super-iron thin film cathodes

An extended conductive matrix facilitates a 100-fold enhancement in charge storage for reversible Fe(III/VI) super-iron thin films. These films were deposited, by electrochemical reduction of Na2FeO4, with an intrinsic high capacity 3 e- cathodic storage of 485 mAh g(-1). Whereas 3 nm Fe(III/VI) films exhibited a high degree of reversibility (throughout 100 charge/discharge cycles), thicker films had been increasingly passive toward the Fe(VI) charge transfer. Films were alternatively deposited on either smooth or on extended conductive matrixes composed of high-surface-area Pt, Ti, and Au and probed galvanostatically and via cyclic voltammetry. A 100 nm Fe(VI) cathode, on the extended conductive matrixes, sustained 100-200 reversible three-electrode charge/discharge cycles, and a 19 nm thin film cathode sustained 500 such cycles. With a metal hydride anode, full cell storage was probed, and a 250 nm super-iron film cathode film sustained 40 charge/discharge cycles, and a 25 nm film was reversible throughout 300 cycles. Fe(VI) salts exhibit higher cathodic capacity and environmental advantages, and the films are of relevance toward the next generation charge storage chemistry for reversible cathodes.     

Formation of Nd<Subscript>1–<Emphasis Type="Italic">x</Emphasis></Subscript>Bi<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>FeO<Subscript>3</Subscript> Nanocrystals under Conditions of Glycine-Nitrate Synthesis

Nd_1–xBi_xFeO₃ nanocrystals with crystallite size 30?60 nm have been prepared under conditions of glycine–nitrate burning. Single-phase Nd_1–xBi_xFeO₃ nanocrystals are formed over the entire studied concentrations range if the glycine–nitrate synthesis is performed in excess of the oxidizer. Under these conditions, a continuous range of the Nd_1–xBi_xFeO₃ solid solutions (0 ≤ х ≤ 0.75) crystallized in the rhombic system (space group Pbnm) are formed without crystallization of the burning intermediates. The Nd_1–xBi_xFeO₃ solid solutions (х = 0.775, 0.8) crystallize in the rhombic system (space group Pbаm).     

Synthesis,characterization, spectroscopic and catalytic oxidation studies of Fe(III), Ni(II), Co(III), V(IV) and U(VI) Schiff base complexes with N,O donor ligands derived from 2,3-diaminopyridine

Fifteen new complexes of transition metals were designed using three Schiff base ligands and aldol condensation of 2,3-diaminopyridine with 5-R-2-hydroxybenzaldehyde (R = F, Cl, Br) in the 1:2 molar ratio. The tetradentate ligands N,N′-bis(5-R-2-hydroxybenzaldehyde) pyridine were acquired with the common formula H₂[(5-R-sal)₂py] and characterized by IR, UV–Vis spectra, ¹H-NMR and elemental analysis. These ligands produce 1:1 complexes M[(5-R-sal)₂py] with Fe(III), Ni(II), Co(III), V(IV) and U(VI) metal ions. The electronic property and nature of complexes were identified by IR, UV–Vis spectra, elemental analysis, X-ray crystallography and cyclic voltammetric methods. The catalytic activity of complexes for epoxidation of styrene with UHP as primary oxidant at minimal temperature (10 °C) has been planned. The spectral data of the ligands and their complexes are deliberate in connection with the structural changes which happen due to complex preparation. The electrochemical outcome has good conformability with what suggested for electronic interaction among metal center and ligand by the UV–Vis and IR measurements.     

Synthesis,Crystal Structure,and Catalytic Property of a Dioxomolybdenum(VI) Complex Derived from <Emphasis Type="Italic">N</Emphasis>'-(3-Bromo-5-Chloro-2-Hydroxybenzylidene)-4-Nitrobenzohydrazide

New dioxomolybdenum(VI) complex [MoO₂(L)(CH₃OH)], where L is the dianionic form of N'- (3-bromo-5-chloro-2-hydroxybenzylidene)-4-nitrobenzohydrazide (H₂L), was prepared and characterized by IR and UV-Vis spectra, as well as single crystal X-ray diffraction (CIF file ССDС no. 1567063). The complex crystallizes as the monoclinic space group P2₁/c with unit cell dimensions a = 13.8471(10), b = 7.5618(6), c = 17.9445(12) Å, β = 90.107(2)°, V = 1878.9(2) ų, Z = 4, R¹ = 0.0821, wR₂ = 0.0907, GOOF = 1.024. X-ray analysis indicates that the complex is a dioxomolybdenum(VI) species with the Mo atom in octahedral coordination. The catalytic oxidation property of the complex with tert-butylhydroperoxide in CH₂Cl₂ was studied.     

Alkali (alkaline-earth) metal,aluminum, and titanium complex orthophosphates: Synthesis and characterization

Phase formation in the A_{1 + x} Al _x Ti_{2 ? x} P₃O₁₂ (A = Li, Na, K, Rb, or Cs; 0 ≤ x ≤ 2.0) and B_{0.5(l + x)}Al _x Ti_{2 ? x} P₃O₁₂ (B = Mg, Ca, Sr, or Ba; 0 ≤ x ≤ 2.0) systems was studied using X-ray powder diffraction, electron probe microanalysis, and IR spectroscopy. The following double and triple orthophosphates were found to exist: A_{1 + x} Al _x Ti_{2 ? x} (PO₄)₃ with A = Li (0 ≤ x ≤ 0.3), Na (0 ≤ x ≤ 1.0), K (x = 0, 1.0, or 2.0), Rb (x = 0, 1.0, or 2.0), or Cs (0 ≤ x ≤ 1.0) and B_{0.5(l + x)}Al _x Ti_{2 ? x} (PO₄)₃ with B = Mg and Ba (x = 0), Ca and Sr (0 ≤ x ≤ 0.2). These orthophosphates crystallize in the structure types of kosnarite, langbeinite, cesium titanium arsenate, potassium aluminum phosphate, or rubidium aluminum phosphate. Their crystal parameters were calculated. For CsTi₂(PO₄)₃ (x = 0), Rietveld refinement was carried out: space group Ia \(\bar 3\) d, Z = 32, a = 19.909(5) Å, V = 7892(1) ų. This compound has a framework structure. The framework is built of TiO₆ octahedra and PO₄ tetrahedra; eight- and 12-coordinated Cs⁺ cations populate interstices.     

Extraction-pyrolytic synthesis and magnetic properties of lanthanum manganites

The synthesis of nanosized manganites LaMnO₃ and La_1–xK_xMnO₃, where x = 0.1, 0.15, 0.185, by low-temperature extraction-pyrolytic method was shown to be promising. Temperature and field dependences for the specific magnetization of the obtained specimens were studied. The dependence of magnetic characteristics on the concentration of doping potassium ion in the studied lanthanum manganites was revealed.     

Synthesis,experimental and theoretical characterization,and antimicrobial studies of some Fe(II), Co(II), and Ni(II) complexes of 2-(4,6-dihydroxypyrimidin-2-ylamino)naphthalene-1,4-dione

The work reported the synthesis and characterisation of Fe²⁺, Co²⁺, and Ni²⁺ complexes of 2-(4,6-dihydroxypyrimidin-2-ylamino)naphthalene-1,4-dione (HL). The spectroscopic and elemental analysis results obtained were consistent with the adoption of the formulas, [ML₂] (M = Fe and Co) and [ML₂(H₂O)] (M = Ni) for the metal complexes. Electronic spectra and magnetic moments of the metal complexes corroborated octahedral geometry for Ni(II) complex and tetrahedral geometry for Fe(II) and Co(II) complexes. However, quantum-chemical calculations using density functional theory predicted trigonal bipyramidal geometry for Ni(II) complex and provided corroborative explanations for the structures of the other complexes. Conductance measurements in dimethylsulfoxide indicate that the complexes are non-electrolytes. The antimicrobial potential of the compounds was evaluated against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Bacillus cereus, Proteus mirabilis, Klebsiella oxytoca, Aspergillus niger, A. flavus, and Rhizopus stolonifer. The compounds gave moderate to good antimicrobial activity. However, the bacterial and fungal organisms were more susceptible to the cobalt complex and ligand respectively than the other compounds at concentration of 10 mg/mL. The compounds were also assessed for their antioxidant potential using 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay. The compounds displayed good DPPH radical scavenging activities. The nickel complex exhibited the best DPPH radical scavenging activity compared to the other compounds.     

Ferrate(VI) and ferrate(V) oxidation of cyanide,thiocyanate, and copper(I) cyanide

Cyanide (CN⁻), thiocyanate (SCN⁻), and copper(I) cyanide (Cu(CN)₄³⁻) are common constituents in the wastes of many industrial processes such as metal finishing and gold mining, and their treatment is required before the safe discharge of effluent. The oxidation of CN⁻, SCN⁻, and Cu(CN)₄³⁻ by ferrate(VI) (Fe^VIO₄²⁻; Fe(VI)) and ferrate(V) (Fe^VO₄³⁻; Fe(V)) has been studied using stopped-flow and premix pulse radiolysis techniques. The rate laws for the oxidation of cyanides were found to be first-order with respect to each reactant. The second-order rate constants decreased with increasing pH because the deprotonated species, FeO₄²⁻, is less reactive than the protonated Fe(VI) species, HFeO₄⁻. Cyanides react 10³–10⁵ times faster with Fe(V) than with Fe(VI). The Fe(V) reaction with CN⁻ proceeds by sequential one-electron reductions from Fe(V) to Fe(IV) to Fe(III). However, a two-electron transfer process from Fe(V) to Fe(III) occurs in the reaction of Fe(V) with SCN⁻ and Cu(CN)₄³⁻. The toxic CN⁻ species of cyanide wastes is converted into relatively non-toxic cyanate (NCO⁻). Results indicate that Fe(VI) is highly efficient in removing cyanides from electroplating rinse water and gold mill effluent.     

Structural investigation of [Au(en)<Subscript>2</Subscript>]Cl(ReO<Subscript>4</Subscript>)<Subscript>2</Subscript> and [Au(en)<Subscript>2</Subscript>](ReO<Subscript>4</Subscript>)<Subscript>3</Subscript> complexes

Novel complex salts [Au(en)₂]Cl(ReO₄)₂ (I) and [Au(en)₂](ReO₄)₃ (II), en = ethylenediamine, are obtained. Their crystal structures are determined by single crystal X-ray diffraction. Complex I crystallizes in the triclinic crystal system: a = 6.2172(7) Å, b = 7.1644(8) Å, c = 8.8829(8) Å, α = 96.605(4)°, β = 110.000(4)°, γ = 97.802(4)°, P-1 space group, Z = 1, d _x = 3.905 g/cm³; complex II crystallizes in the monoclinic crystal system: a = 15.244(2) Å, b = 7.6809(8) Å, c = 9.3476(12) Å, β = 127.004(3)°, C2 space group, Z = 4, d _x = 4.057 g/cm³.     

高铁酸三钾钠的合成及其物理化学性质研究

首次提出了一种在浓的NaOH溶液中电合成0.83 mol•L^－1 Na₂FeO₄溶液进而高纯度合成固态K₃Na(FeO₄)₂的方法. 研究了合成条件, 并利用多种实验技术研究了该固态样品的性质. 实验表明, K₃Na(FeO₄)₂晶体在混合的NaOH-KOH溶液中, 其溶解-沉淀平衡曲线符合经验方程式: [Na^＋][K^＋]³[ ]^2.8＝1.4×10^－4 ([K^＋]≤1.01 mol•L^－1);在浓的KOH溶液中其溶解度与K₂FeO₄几乎一致. 和K₂FeO₄晶体不同, 所得K₃Na(FeO₄)₂晶体显示3个红外特征峰(787, 801～802和858～862 cm^－1)并具有P m1 (164)空间群的六方晶胞, 其粉末在Ar气中直到197 ℃才分解, 热稳定性低于K₂FeO₄.     

Kombination von Ionenaustausch und Gefriertrocknung als Syntheseweg zu neuen Oxoferraten(VI) M2FeO4 mit M = Li,Na, N(CH3)4, N(CH3)3Bzl,N(CH3)3Ph

Combination of Ion Exchange and Freeze Drying as a Synthetic Route to New Oxoferrates(VI) M₂FeO₄ with M = Li, Na, N(CH₃)₄, N(CH₃)₃Bzl, N(CH₃)₃Ph For the first time Oxoferrates(VI) M₂FeO₄ with M = Li, Na, N(CH₃)₄, N(CH₃)₃Bzl and N(CH₃)₃Ph have been prepared by cation exchange reaction on K₂FeO₄ and freeze drying of the resulting aqueous solutions. Li₂FeO₄ crystallizes as a monohydrate and decomposes at –10 ± 3 °C. Na₂FeO₄ crystallizes orthorhombically (Cmcm, a = 5.675(3) Å, b = 9.349(4) Å, c = 7.160(2) Å) and is isostructural to Na₂CrO₄. [N(CH₃)₄]₂FeO₄ crystallizes tetragonally (P4/nbm, a = 11.010(3) Å, c = 10.902(4) Å) and is isostructural to the room temperature modification of [N(CH₃)₄]₂SO₄. Infrared spectra of the alkylammonium ferrates(VI) show a decreasing influence of lattice forces on the vibrations of the FeO₄^2– ions with increasing cation size. Magnetic measurements show the expected paramagnetism for a d² ion.     

Synthesis,structure, and conduction of solid solutions BIMEVOX (Me = Cu,Ti)

Conditions for synthesizing single-phase solid solutions Bi₄V_{2 ? x} Cu _x/2Ti _x/2O_{11 ? x} and Bi_{4 ? x/2}V_{2 ? x/2}Cu _x/2Ti _x/2O_{11 ? x/2} are studied. The sequence of phase transformations is determined. Possible domains of stability of polymorphic modifications and the overall conductivity as a function of temperature and composition are studied. The structure of the γ-modification is refined using Rietveld’s full-profile analysis.