Hexacyanoferrate ion adsorbed on propylpyridiniumsilsesquioxane polymer film-coated SiO2/Al2O3: use in an electrochemical oxidation study of cysteine

Hexacyanoferrate ion, [Fe(CN)₆]⁴⁻, was immobilized by an ion-exchange reaction on the propylpyridiniumsilsesquioxane chloride polymer thin-film-coated SiO₂/Al₂O₃ surface. The amount of [Fe(CN)₆]⁴⁻ immobilized was 0.22 mmol g⁻¹ with a surface coverage of 9.6×10⁻⁶ mmol cm⁻². A carbon paste electrode made with this material was prepared and its electrochemical properties studied. The electrode presented two well-defined redox peaks with midpoint potentials, E_m, of 0.152 V vs SCE. This potential was not significantly affected by pH changes between 2 and 9.5. The electrode showed much reproducible responses and was successfully used to study the electrochemical oxidation of cysteine.     

Cobalt(II) porphyrin complex immobilized on the binary oxide SiO2/Sb2O3: electrochemical properties and dissolved oxygen reduction study

In this work, SiO₂/Sb₂O₃ prepared by the sol-gel processing method, having a specific surface area, S_BET, of 790 m² g⁻¹, an average pore diameter of 1.9 nm and 4.7 wt.% of Sb, was used as substrate base for immobilization of the 5,10,15,20-tetrakis(1-methyl-4-pyridyl)-21H,23H-porphine ion. Cobalt(II) ion was inserted into the porphyrin ring with a yield of complex bonded to the substrate surface of 59.4 μ mol g⁻¹. A carbon paste electrode of this material was used to study, by linear sweeping voltammetric and chronoamperometric techniques, the electrocatalytic reduction of dissolved oxygen. The reduction, at the electrode solid-solution interface, occurred at −0.25 V versus SCE in 1.0 mol l⁻¹ KCl solution, pH 5.5, by a four electron mechanism. The electrode response was invariant under various oxidation-reduction cycles showing that the system is chemically very stable. Such characteristics allowed the study of the electrode response towards various dissolved oxygen concentrations using the chronoamperometry technique. The cathodic peak current intensities plotted against O₂ concentrations, between 1.0 and 12.8 mg l⁻¹, showed a linear correlation. The electrode response time was very fast, i.e. about 1 s. This study was extended using the electrode to determine the concentration of dissolved oxygen in sea water samples.     

Thin films of Cu2Sb and Cu9Sb2 as anode materials in Li-ion batteries

Thin Cu₂Sb films have been prepared by heat-treating Sb films, electrodeposited on Cu substrates. The influence of the electrodeposition conditions and the heat-treatment period on composition and morphology of the films were investigated (SEM and XRD) and the obtained films were tested as anode materials for Li-ion batteries. The Cu₂Sb material showed a stable capacity of 290 mAh g⁻¹ (close to the theoretical capacity of 323 mAh g⁻¹) during more than 60 cycles. The presence of 9-11% (w/w) Sb₂O₃ in the electrodeposited films resulted in smaller particles but also slowed down formation of Cu₂Sb during the heat-treatment step. The presence of Sb₂O₃ was found to decrease the cycling stability although structural reversibility of Cu₂Sb was obtained both with and without Sb₂O₃. Longer heat-treatments of pure Sb films resulted in the formation of Cu₉Sb₂ which was shown to be reduced at a lower potential than Cu₂Sb. The Cu₉Sb₂ was converted to Cu₂Sb during repeated cycling and the capacity of the latter Cu₂Sb material was found to be 230 mAh g⁻¹. While reduction of the materials was complicated by simultaneous formation of an SEI layer, three plateaus could be identified during the oxidation of Li₃Sb, indicating the presence of three separate one-electron oxidation reactions.     

Electrochemical study and complete factorial design of Toluidine Blue immobilized on SiO2/Sb2O3 binary oxide

SiO₂/Sb₂O₃ of specific surface area S _BET = 788 m² g^–1 and 4.7 wt % of Sb was prepared by the sol–gel method. Toluidine Blue (TB⁺) was immobilized on SiO₂/Sb₂O₃ by ion exchange reactions and the amount of dye bonded to the substrate surface was 13.72 mol g^–1 for SiO₂/Sb₂O₃. This material was used to modify carbon paste electrodes and the electrochemical properties of Toluidine Blue (TB⁺) immobilized on a silica surface modified with antimonium trioxide were investigated by cyclic voltammetry. The electron mediator property of toluidine blue was optimized using a factorial design, consisting of four factors each at two levels. Factorial analysis was carried out by searching for better reversibility of the redox process, that is, the lowest separation between anodic and cathodic peak potentials and a current ratio near unity. The aqueous phase pH does not appear to influence the peak separation, E, and the |I _pa//I _pc| current ratio response. The other factors studied, the scan rate, type of electrolyte and electrolyte concentration are important for this chemically modified electrode system demonstrating significant influences on the reversibility of electron transfer. The experimental observations and data analyses on this system indicate that the smallest peak separation occurs using 20 mV s^–1 and 1.0 mol L^–1 KCl while values of |I _pa//I _pc| close to unity are found for 20 mV s^–1 with 1.0 mol L^–1 concentrations of either KCl or CH₃COONa. The electrodes presented reproducible responses and were chemically stable for various oxidation-reduction cycles.     

Synthesis and electrochemical characterization of Pt catalyst supported on Sn0.96Sb0.04O2−δ with a network structure

We synthesized a Pt catalyst supported on Sn_0.96Sb_0.04O_2−δ with a random network structure for the cathode of the polymer electrolyte fuel cell (PEFC). The Sn_0.96Sb_0.04O_2−δ support, synthesized by the flame combustion method, was in the form of nanometer-sized particles with a partially agglomerated structure similar to that of carbon black (CB) and with a high surface area, 125 m² g⁻¹. The structure was considered to be beneficial in reducing the contact resistance between the Sn_0.96Sb_0.04O_2−δ support particles and in dispersing the nanometer-size Pt particles. We applied the nanocapsule method to synthesize the Sn_0.96Sb_0.04O_2−δ-supported Pt catalyst (Pt/Sn_0.96Sb_0.04O_2−δ). The electrochemically active surface area (ECA) of Pt reached a maximum of 60.2 m² g_(Pt)⁻¹, and the high values were maintained during the potential step cycling test (0.9–1.3 V) simulating the start/stop cycling of PEFCs. The oxygen reduction reaction activity of the Pt/Sn_0.96Sb_0.04O_2−δ catalyst exceeded that of Pt supported on carbon black (Pt/CB). We conclude that the random network structured Sn_0.96Sb_0.04O_2−δ might be a good candidate support material for the cathode of PEFCs.     

Synthesis, microstructure, and photocatalysis of In2O3 hollow particles

Indium oxide (In₂O₃) microspheres with hollow interiors have been prepared by a facile implantation route which enables indium ions released from indium-chloride precursors to implant into nonporous polymeric templates in C₂Cl₄ solvent. The templates are then removed upon calcination at 500 °C in air atmosphere, forming hollow In₂O₃ particles. Specific surface area (0.5-260 m² g⁻¹) and differential pore volume (7 × 10⁻⁹ to 3.8 × 10⁻⁴ m³ g⁻¹ Å⁻¹) of the hollow particles can be tailored by adjusting the precursor concentration. For the hollow In₂O₃ particles with high surface area (260 m² g⁻¹), an enhanced photocatalytic efficiency (up to ∼one-fold increase) against methylene blue (MB) dye is obtained under UV exposure for the aqueous In₂O₃ colloids with a dilute solids concentration of 0.02 wt.%.     

Sintering of glass-added BaZn1/3Nb2/3O3 ceramics

The complex perovskite oxide Ba(Zn_1/3Nb_2/3)O₃ (BZN) has been studied for its attractive dielectric properties which place this material interesting for applications as multilayer ceramics capacitors or hyperfrequency resonators. This material is sinterable at low temperature with combined glass phase–lithium salt additions, and exhibits, at 1 MHz very low dielectric losses combined with relatively high dielectric constant and a good stability of this later versus temperature. The 2 wt.% of ZnO–SiO₂–B₂O₃ glass phase and 1 wt.% of LiF-added BZN sample sintered at 900 °C exhibits a relative density higher than 95% and attractive dielectric properties: a dielectric constant ?_r of 39, low dielectrics losses (tan(δ) < 10⁻³) and a temperature coefficient of permittivity τ_? of 45 ppm/°C⁻¹. The 2 wt.% ZnO–SiO₂–B₂O₃ glass phase and 1 wt.% of B₂O₃-added BZN sintered at 930 °C exhibits also attractive dielectric properties (?_r = 38, tan(δ) < 10⁻³) and it is more interesting in terms of temperature coefficient of the permittivity (τ_? = −5 ppm/°C). Their good dielectric properties and their compatibility with Ag electrodes, make these ceramics suitable for L.T.C.C applications.     

Two-step method fabricating high nonlinearity ZnVSb based varistors

A two-step method was introduced to fabricate ZnO–V₂O₅–Sb₂O₃ (ZnVSb) based varistor at low temperatures, such as 900–950 °C. Sb₂O₃/V₂O₅ (V/Sb) precursor was first synthesized and then used to replace Sb₂O₃ as one of the main dopants. The effect of its concentration on the microstructure and electrical properties of the ZnVSb based ceramic was investigated at doping levels up to 1.5 mol%. The microstructural homogeneity of the ceramic was greatly improved by the addition of the precursor. With increasing V/Sb precursor, the average grain size decreased, while the nonlinearity of the as sintered ceramic was enhanced (α_Max = 89). The ZnVSb ceramic is a promising material in the fabrication of multi-layered varistor, in which it could be co-sintered with pure Ag inner electrode.     

Oxidative Dehydrogenation of Ethylbenzene to Styrene with CO2 Over V2O5–Sb2O5–CeO2/TiO2–ZrO2 Catalysts

Utilization of CO₂ as a soft oxidant in the oxidative dehydrogenation of ethylbenzene to styrene, a remarkable V₂O₅–Sb₂O₅–CeO₂/TiO₂–ZrO₂ catalyst has been accomplished. Preparation of TiO₂–ZrO₂ support by co-precipitation followed by a single step deposition of V and Ce and Sb as stabilizers yielded a highly active and selective catalyst. Acid–base and redox properties including sustained stability of active species (V⁵⁺) are responsible for high activity of V₂O₅–Sb₂O₅–CeO₂/TiO₂–ZrO₂ catalyst. The redox cycle is related to the dispersed V⁵⁺ and lattice reduced vanadium site in the VSbO₄ phase. The antimony oxide inhibits the easy redox cycle between different vanadia species.     

Electrodeposition and electrochemical characterisation of thick and thin coatings of Sb and Sb/Sb2O3 particles for Li-ion battery anodes

The possibilities to electrodeposit thick coatings composed of nanoparticles of Sb and Sb₂O₃ for use as high-capacity anode materials in Li-ion batteries have been investigated. It is demonstrated that the stability of the coatings depends on their Sb₂O₃ concentrations as well as microstructure. The electrodeposition reactions in electrolytes with different pH and buffer capacities were studied using chronopotentiometry and electrochemical quartz crystal microbalance measurements. The obtained deposits, which were characterised with XRD and SEM, were also tested as anode materials in Li-ion batteries. The influence of the pH and buffer capacity of the deposition solution on the composition and particle size of the deposits were studied and it is concluded that depositions from a poorly buffered solution of antimony-tartrate give rise to good anode materials due to the inclusion of precipitated Sb₂O₃ nanoparticles in the Sb coatings. Depositions under conditions yielding pure Sb coatings give rise to deposits composed of large crystalline particles with poor anode stabilities. The presence of a plateau at about 0.8 V versus Li⁺/Li due to SEI forming reactions and the origin of another plateau at about 0.4 V versus Li⁺/Li seen during the lithiation of thin Sb coatings are also discussed. It is demonstrated that the 0.4 V plateau is present for Sb coatings for which the (0 1 2) peak is the main peak in the XRD diffractogram.     

Effect of Zr/Ti ratio on piezoelectric properties of Pb(Ni1/3Sb2/3)O3-Pb(ZrTi)O3 ceramics

Piezoceramic compositions [Pb(Ni_1/3Sb_2/3)]_0.02-[Pb(Zr_1−yTi_y)]_0.98O₃ with y = 0.46-0.50 were synthesized by solid state route to study the effect of Zr/Ti ratio on crystal structure, microstructure, piezoelectric and dielectric properties. Calcination was performed at 1060 °C. The specimens were sintered at 1280 °C for 1 h. X-ray diffraction studies indicate the co-existence of tetragonal and rhombohedral perovskite phases in these compositions. Microstructural analysis showed the dense and uniform microstructure for [Pb(Ni_1/3Sb_2/3)]_0.02-[Pb(Zr_0.52Ti_0.48)]_0.98O₃. This composition was resulted in optimum values of properties viz. charge constant (d₃₃ = 301 × 10⁻¹² C/N), voltage constant (g₃₃ = 33.7 × 10⁻³ V m/N), product of piezoelectric charge constant and voltage constant (d₃₃ × g₃₃ = 10.12 × 10⁻¹² C V m/N²) and coupling factor (k_p = 0.63). Results indicated that this material composition could be suitable for power harvesting and sensor applications.     

Sb2O3–ZnO nanospindles: A potential material for photocatalytic and sensing applications

This paper reports the facile synthesis, characterization and applications of Sb₂O₃–ZnO nanospindles. The nanospindles were synthesized by facile diethanolammine assisted hydrothermal process and characterized in detail in terms of their morphological, structural, compositional and optical properties. The detailed characterizations revealed that the prepared nanoellipsoids are well-crystalline, grown in high density and possessing good optical properties. Further, the as-synthesized Sb₂O₃–ZnO nanospindles were found to be an efficient photocatalyst for the degradation of methylene blue (MB) dye under UV light. Sb₂O₃–ZnO nanospindles were also used as an efficient electron mediator to fabricate a robust, highly sensitive and reproducible chemical sensor for the detection of thiourea in aqueous medium. The fabricated chemical sensor possesses high sensitivity of 6.54 µA mmol L⁻¹ cm⁻². The sensing calibration plot was found to be linear (R²=0.91423) over the large concentration range from 1.56 mmol L⁻¹ to 100 mmol L⁻¹. The obtained results confirmed that the Sb₂O₃–ZnO nanospindles may hold great potential for the removal of organic pollutants and for monitoring of thiourea in aqueous solution.     

Transparent zinc silicate/ zinc oxide crystallized glass-ceramics for water remediation application under visible light

The present study focuses on taking advantage of both Zinc Silicate (Zn₂SiO₄) and Zinc Oxide (ZnO) crystals in the glass matrix for enhancing photocatalytic activity. The fabricated samples were used as a photocatalyst for degrading ～ 5 mg/L concentrated “Methylene Blue” (MB) and “Rhodamine B” (RB) dye separately under visible light. For this, 44 SiO₂:11 Al₂O₃:35 ZnO:10 K₂O compositions were prepared via the traditional melt quench process followed by heat treating at a temperature of 750 °C at 2, 4, and 6 h. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) was employed to characterize the fabricated samples. The bandgap measured from Differential reflectance spectroscopy (DRS) was found to decrease with an increase in the heat treatment duration. 44 SiO₂:11 Al₂O₃:35 ZnO:10 K₂O composition heat-treated at 750 °C for 2 h degraded ～59% and ～71% of Rhodamine B (RB) dye and Methylene Blue (MB) dye under visible light in 4 h.     

Study on the rapid synthesis of LiNi1−xCoxO2 cathode material for lithium secondary battery

LiNi_1−xCo_xO₂ (x = 0, 0.1, 0.2) cathode materials were successfully synthesized by a rheological phase reaction method with calcination time of 0.5 h at 800 °C. All obtained powders are pure phase with α-NaFeO₂ structure (R-3m space group). The samples deliver an initial discharge capacity of 182, 199 and 189 mAh g⁻¹ (25 mA g⁻¹, 4.35-3.0 V), respectively. The reaction mechanism was also discussed, which consists of a series of defect reactions. As a result of these defect reactions, the reaction of forming LiNi_1−xCo_xO₂ takes place in high speed.     

Preparation and characterization of Bi-doped antimony selenide thin films by electrodeposition

Bi-doped antimony selenide (Sb_2−xBi_xSe₃) thin films have been prepared by potentiostatical electrodeposition and post annealing treatment. Cyclic voltammetry (CV) was used to investigate the electrochemical behaviors of electrodeposition. The suitable deposition potential for film preparation was determined to be about −0.40 V vs. SCE combining with CV, energy dispersive X-ray spectroscopy (EDS), environmental scanning electron microscope (ESEM) studies. After annealing, film shows improved crystallinity and a basic orthorhombic Sb₂Se₃ structure but having a larger d-spacing due to the substitution of Bi for Sb in Sb₂Se₃ lattice. The annealed film exhibits an absorption coefficient of larger than 10⁵ cm⁻¹ in the visible region, an direct optical band gap of 1.12 ± 0.01 eV, the n-type conductivity, an carrier concentration of 1.1 × 10¹⁹ cm⁻³ and an flat band potential of −0.40 ± 0.03 V vs. SCE.     

Structural and electrochemical behaviors of metastable Li2/3[Ni1/3Mn2/3]O2 modified by metal element substitution

Layered metastable lithium manganese oxides, Li_2/3[Ni_1/3−xMn_2/3−yM_x+y]O₂ (x = y = 1/36 for M = Al, Co, and Fe and x = 2/36, y = 0 for M = Mg) were prepared by the ion exchange of Li for Na in P2-Na_2/3[Ni_1/3−xMn_2/3−yM_x+y]O₂ precursors. The Al and Co doping produced the T^#2 structure with the space group Cmca. On the other hand, the Fe and Mg doped samples had the O6 structure with space group R-3m. Electron diffraction revealed the 1:2 type ordering within the Ni_1/3−xMn_2/3−yM_x+yO₂ slab. It was found that the stacking sequence and electrochemical performance of the Li cells containing T^#2-Li_2/3[Ni_1/3Mn_2/3]O₂ were affected by the doping with small amounts of Al, Co, Fe, and Mg. The discharge capacity of the Al doped sample was around 200 mAh g⁻¹ in the voltage range between 2.0 and 4.7 V at the current density of 14.4 mA g⁻¹ along with a good capacity retention. Moreover, for the Al and Co doped and undoped oxides, the irreversible phase transition of the T^#2 into the O2 structure was observed during the initial lithium deintercalation.     

Electrodeposition of P-type BixSb2−xTey thermoelectric film from dimethyl sulfoxide solution

The electrochemical behaviors of Bi(III), Te(IV), Sb(III) and their mixtures in DMSO solutions were investigated using cyclic voltammetry and linear sweep voltammetry measurements. On this basis, Bi_xSb_2−xTe_y film thermoelectric materials were prepared by potentiodynamic electrodeposition technique from mixed DMSO solution, and the compositions, structures, morphologies as well as the thermoelectric properties of the deposited films were also analyzed. The results show that Bi_xSb_2−xTe_y compound can be prepared in a very wide potential range by potentiodynamic electrodeposition technique in the mixed DMSO solutions. After anneal treatment, the deposited film prepared in the potential range of −200 to −400 mV shows the highest Seebeck coefficient (185 μV/K), the lowest resistivity (3.34 × 10⁻⁵ Ω m), the smoothest surface, the most compact structure and processes the stoichiometry (Bi_0.49Sb_1.53Te_2.98) approaching to the Bi_0.5Sb_1.5Te₃ ideal material most. This Bi_0.49Sb_1.53Te_2.98 film is a kind of nanocrystalline material and (0 1 5) crystal plane is its preferred orientation.     

Effects of Sb content on electrical properties of lead-free piezoelectric (K0.4425Na0.52Li0.0375) (Nb0.9625−xSbxTa0.0375)O3 ceramics

Lead-free (K_0.4425Na_0.52Li_0.0375) (Nb_0.9625−xSb_xTa_0.0375)O₃ piezoelectric ceramics were prepared by the conventional sintering method. The effects of the Sb content on the phase structure, microstructure, dielectric, piezoelectric, and ferroelectric properties of the (K_0.4425Na_0.52Li_0.0375) (Nb_0.9625−xSb_xTa_0.0375)O₃ ceramics were investigated. The much higher Pauling electronegativity of Sb compared with Nb makes the ceramics more covalent. By increasing x from 0.05 to 0.09, all samples exhibit a single perovskite structure with an orthorhombic phase over the whole compositional range, and the bands in the Raman scattering spectra shifted to lower frequency numbers. The grain growth of the ceramics was improved by substituting Sb⁵⁺ for Nb⁵⁺. Significantly, the (K_0.4425Na_0.52Li_0.0375) (Nb_0.8925Sb_0.07Ta_0.0375)O₃ ceramics show the peak values of the piezoelectric coefficient (d₃₃), electromechanical coupling coefficient (k_p), and dielectric constant (?), which are 304 pC/N, 48% and 1909, respectively, owing to the densest microstructure of typical bimodal grain size distributions. Besides, the underlying mechanism for variations of the electrical properties due to Sb⁵⁺ substitution was explained in this work.     

Effect of Cr dopant on the cathodic behavior of LiCoO2

Compounds of the formula LiCo_1−yCr_yO₂ (0.0≤y≤0.20 and y=1.0) have been synthesized by high temperature solid-state reaction and were characterized by XRD and FT-IR. Hexagonal a and c lattice parameters increase with increasing y as expected from ionic size effects. Cyclic voltammograms reveal that the phase transformation occurring at x=0.5 in Li_1−x(Co_1−yCr_y)O₂ is suppressed for y=0.05 and 0.10. Low-current (0.01 C; 1 C=140 mA g⁻¹) galvanostatic charging curves show that the deintercalation voltage for y=0.05 and 0.10 decrease for a given x as compared to LiCoO₂. Galvanostatic charge-discharge cycling of the Li(Co_1−yCr_y)O₂ cathodes at 0.14 C and 2.7-4.3 V (vs. Li) show that increasing amount of chromium content in the LiCoO₂ lattice drastically reduces the amount of Li that can be reversibly cycled. Ex-situ XRD of the cycled cathodes show that slight cation-mixing occurs in the layered structure for y=0.05 and 0.10 and could be the reason for their poor electrochemical performance. Reversible Li intercalation/deintercalation is not possible in LiCrO₂ in the voltage range 2.7-4.3 V.