Electrochemical deposition of Bi<Subscript>2</Subscript>Te<Subscript>3</Subscript> for thermoelectric microdevices

The electrolyses of solutions of bismuth oxide and tellurium oxide in nitric acid with molar ratios of Bi:Te=3:3–4:3 lead to cathodic deposits of films of bismuth telluride (Bi₂Te₃), an n-type semiconductor. Current densities of 2–5 mA/cm² were applied. Voltammetric investigations showed that Bi₂Te₃ deposition occurred at potentials more negative than −0.125 V (Ag/AgCl, 3 M KCl). The deposit was identified as bismuth telluride (γ-phase) by X-ray analysis. Hall-effect measurements verified the n-type semiconducting behaviour. The films can be deposited in microstructures for thermoelectric microdevices like thermoelectric batteries or thermoelectric sensors.     

Production of 1,3-Butadiene From C4 Raffinate-3 Through Oxidative Dehydrogenation of n-Butene Over Bismuth Molybdate Catalysts

Recent progress on the bismuth molybdate catalysts for oxidative dehydrogenation of n-butene to 1,3-butadiene was reported in this review. A number of bismuth molybdate catalysts, including pure bismuth molybdates (α-Bi₂Mo₃O₁₂, β-Bi₂Mo₂O₉, and γ-Bi₂MoO₆) and multicomponent bismuth molybdates, were prepared by a co-precipitation method for use in the production of 1,3-butadiene from C₄ raffinate-3 through oxidative dehydrogenation of n-butene. It was observed that multicomponent bismuth molybdate catalyst was more efficient than pure bismuth molybdate catalyst in the oxidative dehydrogenation of n-butene. Various experimental measurements such as temperature-programmed reoxidation, X-ray photoelectron spectroscopy, and O₂-temperature-programmed desorption analyses were carried out to elucidate the different catalytic activity of bismuth molybdate catalysts. It was revealed that a bismuth molybdate catalyst with a higher oxygen mobility showed a better catalytic performance in terms of conversion of n-butene and yield for 1,3-butadiene. We have successfully demonstrated from experimental findings that oxygen mobility of bismuth molybdate catalyst played a key role in determining the catalytic performance in the oxidative dehydrogenation of n-butene to 1,3-butadiene.     

Synthesis and thermal decomposition of lanthanide hexacyanochromate(iii) complexes,Ln[Cr(CN)6]·nH2O (Ln=La-Lu; n=3, 4)

New solid complex of nitrilotriacetic acid and bismuth trichloride was synthesized by a solid phase reaction of nitrilotriacetic acid and bismuth trichloride at room temperature. The composition of the sample is BiCl₃[N(CH₂COOH)₃]_2.5. The crystal structure of the complex belongs to triclinic system with the lattice parameters: α=0.7849 nm, β=0.9821 nm, χ=2.0021 nm, α=96.50°, β=98.76° and γ=90.49°. The far-infrared spectra show the bonding between the Bi ion and N atom of nitrilotriacetic acid. The thermal analysis also demonstrates the complex formation between the bismuth ion and nitrilotriacetic acid. The gaseous pyrolysis product and the final residue in the thermal decomposition process are determined to check the thermal decomposition reaction. This revised version was published online in August 2006 with corrections to the Cover Date.     

Electrochemical modification of Bi2S3 coatings in a nickel plating electrolyte

The electrochemical behavior of Bi₂S₃ coatings in Watts nickel plating electrolyte was investigated using the cyclic voltammetry, electrochemical quartz crystal microbalance, X-ray diffraction, and energy dispersive X-ray analysis methods. During the bismuth sulfide coating reduction in Watts background electrolyte in the potential region from −0.4 to −0.6 V, the Bi₂S₃ and Bi(III) oxygen compounds are reduced to metallic Bi, and the decrease in coating mass is related to the transfer of S²⁻ ions from the electrode surface. When the bismuth sulfide coating is reduced in Watts nickel plating electrolyte, the observed increase in coating mass in the potential region −0.1 to −0.4 V is conditioned by Ni²⁺ ions reduction before the bulk deposition of Ni, initiated by Bi₂S₃. In this potential region, the reduction of Bi(III) oxygen compounds can occur. After the treatment of as-deposited bismuth sulfide coating in nickel plating electrolyte at E = −0.3 V, the sheet resistance of the layer decreases from 10¹³ to 500–700 Ω cm. A metal-rich mixed sulfide Ni₃Bi₂S₂–parkerite is obtained when as-deposited bismuth sulfide coating is treated in Watts nickel plating electrolyte at a potential close to the equilibrium potential of the Ni/Ni²⁺ system and then annealed at temperatures higher than 120 °C.     

Heterogeneous selective oxidation of formaldehyde on oxide catalysts:In situ FTIR study of formaldehyde surface species on a V-Ti-O catalyst and oxygen effect

The interaction of formaldehyde with a highly selective V-Ti-O catalyst for the oxidation of formaldehyde to formic acid is studied by Fourier-transform infrared (FTIR) spectroscopy at 70–200‡C. In a flow of formaldehyde/oxygen mixture and in a mixture without oxygen at optimal temperatures for formic acid formation (100–140‡C), methoxy groups and other oxygenates are formed in small amounts. These are two bidentate formates and covalently bound monodentate formate. The fact that similar oxygenates are observed independently of the presence of oxygen in the reaction mixture suggests the participation of the catalyst oxygen in their formation. Oxygen accelerates the desorption of bidentate formates. Bidentate formates of one type decompose in a flow of air at 100–150‡C, and bidentate formates of the other type decompose at 170–200‡C.     

Synthesis and structure of bismuth 8-quinoline-selenolate Bi(C<Subscript>9</Subscript>H<Subscript>6</Subscript>NSe)<Subscript>3</Subscript>

Bismuth 8-quinolineselenolate Bi(C₉H₆NSe)₃ was synthesized. The molecular and crystal structure of this compound was determined by X-ray diffraction structural analysis. The effect of replacing the ligand atoms Se→S and the role of the unshared electron pair on the formation of the coordination polyhedron of the central bismuth atom in bismuth(III) 8-quinolineselenolate and bismuth(III) 8-quinolinethiolate, which are complexes of a Group V p-element in an incomplete valence state was discussed. Dedicated to the memory of Academician Yurii Bankovsky, the founder of the chemistry of 8-mercaptoquinoline (December 22, 1927–January 28, 2003) on the occasion of the eightieth anniversary of his birth. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1866–1874, December, 2007.     

Kinetic regularities of thermal transformations in nanosized bismuth films

Transformations in a nanosized bismuth layer are studied by means of optical spectroscopy, microscopy, and gravimetry, depending on the thickness (d = 3–120 nm), thermal treatment temperature (T = 373–673 K) and time (τ] = 0.05–2500 min). It is established that, depending on the initial thickness of the bismuth films and the thermal treatment temperature, the kinetic curves of the degree of transformation are satisfactorily described within linear, inverse logarithmic, cubic, and logarithmic laws. The contact potential difference for the Bi, Bi₂O₃ films and the photo-electromotive force for the Bi-Bi₂O₃ systems is measured. An energy-band diagram for the Bi-Bi₂O₃ systems is constructed. A model for the thermal transformation of Bi films that includes the stage of oxygen adsorption, the redistribution of charge carriers in the Bi-Bi₂O₃ contact field, and the formation of bismuth(III) oxide is proposed.     

An amino acid based system for CO2 capture and catalytic utilization to produce formates

Herein, we report a novel amino acid based reaction system for CO₂ capture and utilization (CCU) to produce formates in the presence of the naturally occurring amino acid l-lysine. Utilizing a specific ruthenium-based catalyst system, hydrogenation of absorbed carbon dioxide occurs with high activity and excellent productivity. Noteworthy, following the CCU concept, CO₂ can be captured from ambient air in the form of carbamates and converted directly to formates in one-pot (TON > 50 000). This protocol opens new potential for transforming captured CO₂ from ambient air to C1-related products.

A novel amino acid based reaction system for CO₂ capture and utilization (CCU) to produce formates is presented applying a ruthenium-based catalyst. Noteworthy, CO₂ can be captured from ambient air and converted to formates in one-pot (TON > 50 000).     

Interaction of oxygen with an Si(001) surface coated with bismuth

Ionization and Auger spectroscopy show that a submonolayer coating of bismuth on Si(001) reduces the initial attachment coefficient for molecular oxygen by comparison with a clean Si(001) surface by two orders of magnitude, while exposure to >10⁵ Langmuir of O₂ causes bismuth to stimulate the formation of surface silicon oxide having stoichiometry close to SiO₂. Taras Shevchenko Kiev University, 64 ul. Vladimirskaya, Kiev 17, Ukraine 252601. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 33, No. 2, pp. 124–127, March–April, 1997.     

Equilibrium distribution of lanthanum,neodymium, and thorium between fluoride salt melts and liquid bismuth

The extraction of lanthanum, neodymium, and thorium from 73LiF-27BeF₂, 78LiF-22ThF₄, 75LiF-5BeF₂-20ThF₄, 15LiF-58NaF-27BeF₂, and 60LiF-40NaF (mol %) fluoride salt melts into liquid bismuth with admixtures of lithium as a reducing agent was studied at 580–750°C. Equilibrium values of their distribution coefficients were measured. Beryllium as distinct from neodymium and lanthanum almost was not extracted into bismuth from salt beryllium-containing compositions. A decrease in the mole fraction of LiF in LiF-BeF₂ melts substantially increased the effectiveness of its purification from lanthanides. The LiF-ThF₄ and LiF-BeF₂-ThF₄ salt mixtures with comparatively high thorium concentrations (≥20–22 mol %) could not be used for effective separation of lanthanides and thorium in a system for extraction processing of fuel salts.     

Synthesis and characterization of antimony trichloride and bismuth trichloride complexes with valine

Two compounds of antimony trichloride and bismuth trichloride with valine are synthesized by solid phase synthesis at room temperature. Their compositions, determined by element analysis, are Sb(C₅H₁₀O₂N)₃·2H₂O and Bi(C₅H₁₀O₂N)₂Cl·0.5H₂O. The crystal structure of antimony complex with valine belongs to triclinic system and its lattice parameters are: a=0.9599 nm, b=1.5068 nm, c=1.9851 nm, α=92.270, β=95.050, γ=104.270. The crystal structure of bismuth complex with valine belongs to monoclinic system and its lattice parameters are: a=1.6012 nm, b=1.8941 nm, c=1.839 nm, β=99.73°. The far-infrared spectra and infrared spectra show that the amino group and carboxyl of valine may be coordinated to antimony and bismuth, respectively, in two compounds. The TG-DSC results also reveal that the complexes were formed.     

Synthesis and structure of bismuth(III) oxohydroxocarboxylates

The structure and thermal transformation of bismuth(III) oxohydroxocarboxylates Bi₆O₄(OH)₄(C _n H_{2n − 1}O₂)₆, where (C _n H_{2n − 1}O₂) is a carboxylate ion and n = 2 (2–9, 11), were studied by X-ray powder diffraction, thermogravimetry, IR spectroscopy, and chemical analysis. The conditions of precipitation of bismuth carboxylates from perchlorate solutions were determined. The compounds have a layered structure and undergo the same phase transformations on heating.     

Dependence of the energy of surface-active substances/metal interaction on their ionization potentials. Evaluation of hydrophilicity of metal

The function Δ(ΔG _A ⁰), which is the difference of Gibbs energies characterizing surface-active substance (surfactant, SAS) adsorption at metal/solution and air/solution surfaces, has been introduced. The equation connecting the function Δ(ΔG _A ⁰) with SAS ionization potential has been obtained using the elementary theory of donor-acceptor interactions. Published experimental data on SAS adsorption at mercury, bismuth and gold have been used for Δ(ΔG _A ⁰) calculation. The dependence of Δ(ΔG _A ⁰) on ionization potentials can be described by an equation derived in this work. It has been demonstrated that the value of the hydrophilicity of gold is much higher than the values for mercury and bismuth. The lifetime of SAS molecules at a metal surface has been estimated. The question of the possibility of theoretica l estimation of standard energies ΔG _A ⁰ characterizing SAS adsorption at a metal/solution surface has been discussed. Received: 9 December 1996 / Accepted: 13 January 1997     

Solid Phase Synthesis, Characterization of Hexamethylenetetramine Complexes of Antimony and Bismuth Trichloride

New hexamethylenetetramine complexes of antimony and bismuth trichloride were synthesized through a solid phase reaction of hexamethylenetetramine and antimony or bismuth trichloride. The formula of the complex is MCl₃(C₆H₁₂N₄)₂⋅H₂O (M=Sb, Bi).The crystal structure of the complexes belongs to monoclinic system and the lattice parameters: a=1.249 nm, b=1.4583 nm, c=1.6780 nm andβ=91.78° for SbCl₃(C₆H₁₂N₄)₂⋅H₂O and a=1.3250 nm, b=1.3889 nm, c=1.7449 nm and β=98.94° for BiCl₃(C₆H₁₂N₄)₂⋅H₂O. Far-infrared spectra reveal that the antimony or bismuth ion is coordinated by the nitrogen atom of the hexamethylenetetramine. The thermal analysis also demonstrates the complex formation between the antimony or bismuth ion and hexamethylenetetramine. The intermediate and final residues in the thermal decomposition process have been analyzed to check the pyrolysis reaction. This revised version was published online in August 2006 with corrections to the Cover Date.     

Catalytic activity of nanosized Co-Cu oxide systems in the deep oxidation of methane

The effect of the composition of nanosized catalysts, produced by thermal decomposition of Co(II) and Cu(II) formates deposited on ZrO₂, SBA-15, and MCM-41, on their activity in the deep oxidation of methane was investigated. It was shown that the activity of the catalyst depends on the nature of the support and on the Co/Cu ratio. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 41, No. 6, pp. 331–335, November–December, 2005.     

Investigation of synthesis and microstructure of bismuth titanates with TiO<Subscript>2</Subscript> rich compositions

Preliminary examinations regarding formation of bismuth titanates in a part of Bi₂O₃—TiO₂ system rich with TiO₂ have been carried out. Bismuth titanates have been synthesized from mixtures of Bi₂O₃ and TiO₂ (anatase) by the conventional solid-state method at the temperatures ranged from 1273 to 1473 K. Differential thermal analysis (DTA), powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) have been used to study the formation of bismuth titanates. The following compounds have been achieved: Bi₄Ti₃O₁₂, Bi₂Ti₂O₇ and Bi₂Ti₄O₁₁. Existence of controversial bismuth titanate of formula Bi₂Ti₃O₉ in the Bi₂O₃—TiO₂ system has not been confirmed.     

Formation of bismuth(III) N-methylthiourea complexes in aqueous solutions

The formation constants of bismuth(III) methylthiourea complexes in aqueous solution were determined at 298 K and an acidity of 2 M HClO₄ using the “ligand-oxidized ligand species” potentiometric method and the methylthiourea (mtu)-symmetric dimethylformamidine disulfide (mFDS) redox pair. The formation function was obtained, and the conditional (β _n ^*) and true (β _n ) formation constants of Bi(mtu) _n ³⁺ (1 ≤ n ≤ 8) were calculated. The value of β₁ and the formation of complexes with coordination numbers higher than six was confirmed by spectrophotometry.     

Selective Metal‐Free Hydrosilylation of CO2 Catalyzed by Triphenylborane in Highly Polar,Aprotic Solvents

Triphenylborane (BPh₃) in highly polar, aprotic solvents catalyzes hydrosilylation of CO₂ effectively under mild conditions to provide silyl formates with high chemoselectivity (>95 %) and without over‐reduction. This system also promotes reductive hydrosilylation of tertiary amides as well as dehydrogenative coupling of silane with alcohols.     

Structural characterization of amorphous and nanostructured bismuth silicate xerogels

Bismuth silicate xBi₂O₃·(1 − x)SiO₂ xerogels, 0 ≤ x ≤ 0.5, doped with gadolinium have been synthesized by sol–gel method. The study aims to evidence by X-ray diffraction (XRD), electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) the structural changes in amorphous Bi₂O₃–SiO₂ xerogels, function of Bi₂O₃ content and heat treatment. As was proved by XRD, nanostructured samples were obtained after 30 min heat treatment at 400 °C of the as-prepared samples with x > 0, in the mainly amorphous matrices nanocrystals of Bi_5.6Si_0.5O_9.4 phase being developed. The dimension of the nanocrystallites are function of the bismuth content, and vary from few nanometers to 25 nm for samples with x = 0.14 and x = 0.5 respectively. The local order around silicon, reflected by 29Si MAS NMR spectra, is less dependent on both composition and thermal history of the samples, showing that an amorphous silicon rich phase is present in all samples. The changes in the local order around Gd³⁺ ions, as reflected by the EPR spectra dependence on composition and especially on the heat treatment, support the assumption that a part of these paramagnetic ions is incorporated in the bismuth rich phase.     

Research on the electrochemistry of oxygen ion conductors in the former Soviet Union

Following previous reviews of research results on oxygen ion-conducting materials obtained in the former USSR, this article addresses the case of Bi₂O₃-based compositions. Phase formation in oxide systems with Bi₂O₃, thermal expansion, stability, bulk transport properties and oxygen exchange of bismuth oxide solid electrolytes are briefly discussed. Primary attention is focused on oxides with high ionic and mixed conductivity, including stabilized fluorite-type (δ) and sillenite (γ) phases of Bi₂O₃, γ-Bi₄V₂O₁₁ and other compounds of the aurivillius series. Another major point being addressed is on the applicability of these materials in high-temperature electrochemical cells, which is limited by numerous specific disadvantages of Bi₂O₃-based ceramics. The electrochemical properties of various electrode systems with bismuth oxide electrolytes are also briefly analyzed. Electronic Publication