Diagnostics of Plasma Behavior and TiO<Subscript>2</Subscript> Properties Based on DBD/TiO<Subscript>2</Subscript> Hybrid System

Plasma catalysis is gaining increasing interest in environmental and energy applications, such as the destruction of gas pollutants and hydrocarbon conversion. In order to further improve the application of plasma catalysis, it is crucial to understand the fundamental mechanisms, especially the mutual interaction between plasma and catalyst. In this paper, a parallel-plate dielectric barrier discharge (DBD) reactor is developed to investigate the plasma behavior and TiO₂ properties in the plasma/catalytic hybrid system. The introduction of TiO₂ thin film coated on the dielectric improves the discharge intensity, which significantly contributes to the enhancement of reactive species and charges. The energy efficiency of generating ozone in DBD/TiO₂ system has been approximately raised by 38% compared to pure DBD when the applied voltage reaches 13 kV. It is fortunately found that the discharge does not change the crystal structure of the TiO₂, but the band gap increases from 3.13 to 3.39 eV, which has been proved to enhance the oxidizability of TiO₂ in the degradation of methyl orange experiment under UV light. The FTIR and XPS spectra also demonstrate that N element is doped into the structure of TiO₂. These results successfully illustrate the plasma behavior and catalyst properties in plasma/catalysis hybrid system and provide reference for the optimization of the plasma catalysis process.     

Nonstoichiometric Zn Ferrite and ZnFe<Subscript>2</Subscript>O<Subscript>4</Subscript>/Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> Composite Spheres: Preparation,Magnetic Properties,and Chromium Removal

Monodisperse and porous nonstoichiometric Zn ferrite can be prepared by a solvothermal method. Such non-Zn ferrite was used to be the precursor for synthesis of ZnFe₂O₄/Fe₂O₃ composite via calcination at 600°C for 3 h in air. X-ray powder diffractometer (XRD) and Energy Dispersive Spectrometer (EDS) proved the nonstoichiometry of Zn ferrite synthesized by solvothermal method and the formation of ZnFe₂O₄/Fe₂O₃ composite via calcination. TEM image showed that non-Zn ferrite spheres with wormlike nanopore structure were made of primary nanocrystals. BET surface area of non-Zn ferrite was much higher than that of ZnFe₂O₄/Fe₂O₃ composite. Saturation magnetization of non-Zn ferrites was significantly higher than that of ZnFe₂O₄/Fe₂O₃ composites. Calcination of non-Zn ferrite resulted in the formation of large amount of non-magnetic Fe₂O₃,which caused a low magnetization of composite. Because of higher BET surface area and higher saturation magnetization, non-Zn ferrite presented better Cr⁶⁺ adsorption property than ZnFe₂O₄/Fe₂O₃ composites.     

Viscous Flow of Concentrated Aqueous Solutions of NiCl<Subscript>2</Subscript> + FeCl<Subscript>2</Subscript>

The dynamic viscosity, apparent molar volume, enthalpy, and Gibbs energy of activation of a viscous flow of concentrated aqueous solutions of NiCl₂ + FeCl₂ were calculated. The concentration dependences of these parameters were analyzed in terms of structural transformations. A polynomial approximation of the concentration dependences of the dynamic viscosity of the solutions under study was performed using MATLAB 6.1 software package.     

Thermochemical Properties of Dissolution of Nicotinic Acid C<Subscript>6</Subscript>H<Subscript>5</Subscript>NO<Subscript>2</Subscript>(s) in Aqueous Solution

Nicotinic acid (also known as niacin) was recrystallized from anhydrous ethanol. X-ray crystallography was applied to characterize its crystal structure. The crystal belongs to the monoclinic system, space group P2₍₁₎/c. The crystal cell parameters are a = 0.71401(4) nm, b = 1.16195(7) nm, c = 0.71974(6) nm, α = 90°, β = 113.514(3)°, γ = 90° and Z = 4. Molar enthalpies of dissolution of the compound, at different molalities m/(mol·kg^?1) were measured with an isoperibol solution–reaction calorimeter at T = 298.15 K. The molar enthalpy of solution at infinite dilution was calculated, according to Pitzer’s electrolyte solution model and found to be \( \Delta_{\text{sol}} H_{m}^{\infty } = ( 2 7. 3 \pm 0. 2) \) kJ·mol^?1 and Pitzer’s parameters (\( \beta_{{\text{MX}}}^{{\text{(0)}L}} \), \( \beta_{{\text{MX}}}^{{\text{(1)}L}} \) and \( C_{{\text{MX}}}^{\phi L} \)) were obtained. The values of apparent relative molar enthalpies (\( {}^{\phi }L \)) and relative partial molar enthalpies (\( \overline{{L_{2} }} \) and \( \overline{{L_{1} }} \)) of the solute and the solvent at different molalities were derived from the experimental enthalpy of dissolution values of the compound. Also, the standard molar enthalpy of formation of the anion \( {\text{C}}_{ 6} {\text{H}}_{ 4} \text{NO}_{2}^{-} \) in aqueous solution was calculated to be \( {\Delta_{\text{f}}^{} H}_{\text{m}}^{\text{o}} ({\text{C}}_{ 6} {\text{H}}_{ 4} {\text{NO}}_{2}^{-} \text{,aq}) = - \left( {603.2 \pm 1.2} \right)\;{\text{kJ}}{\cdot}{\text{mol}}^{-1} \).     

Preparation,Thermal Behaviour,and Crystal Structure of MgAl<Subscript>2</Subscript>F<Subscript>8</Subscript>(H<Subscript>2</Subscript>O)<Subscript>2</Subscript>

Summary.  Single crystals of MgAl₂F₈(H₂O)₂ have been obtained under hydrothermal conditions (250°C, 14 d) from a starting mixture of AlF₃ and MgAlF₅(H₂O)₂ in a 5% (w/w) HF solution. The crystal structure has been determined and refined from single crystal data (Fmmm (#69), Z = 4, a = 7.2691(7), b = 7.0954(16), c = 12.452(2) ?, 281 structure factors, 27 parameters, R(F ² > 2σ (F ²)) = 0.0282, wR(F ² all) = 0.0885). The obtained crystals were systematically twinned according to (010/100/001) as twinning matrix, reflecting the pseudo-tetragonal metric. The crystal structure is composed of perowskite-type layers built of corner sharing AlF₆ octahedra with an overall composition of AlF₄ ⁻ which are connected via common fluorine atoms of [MgF_4/2(H₂O)_2/1] octahedra. Group-subgroup relations of MgAl₂F₈(H₂O)₂ to WO₃(H₂O)_0.33 and to other M(II)M(III)₂ F₈(H₂O)₂ structures are briefly discussed. Above 570°C, MgAl₂F₈(H₂O)₂ decomposes under elimination of water into α-AlF₃, β-AlF₃, and MgF₂. Received October 29, 2001. Accepted (revised) December 6, 2001     

Oxidation of Diethyl Sulfide in Aqueous Solutions by Peroxynitrite and the H<Subscript>2</Subscript>O<Subscript>2</Subscript>-NO<Stack><Subscript>2</Subscript><Superscript>−</Superscript></Stack> System

It was found that nitrite anions are effective activators of hydrogen peroxide in the reaction with diethyl sulfide. The observed kinetics are consistent with the proposed intermediate formation of peroxynitrous acid (ONOOH). The rate constants for the reaction of diethyl sulfide Et₂S with the acid ONOOH (k₀ = 1.8⋅10³ L/mol⋅s) and with the anion ONOO⁻ (k₋ = 6⋅10⁻² L/mol⋅s) are respectively 10⁵ and three times higher than with hydrogen peroxide. __________ Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 41, No. 5, pp. 290–295, September–October, 2005.     

Preparation of Aqueous Colloidal Dispersion of C<Subscript>60</Subscript> Fullerene

A method for preparing aqueous colloidal dispersions of C₆₀ fullerene free of organic solvents is proposed. The size of dispersed particles is determined using the turbidity spectra. A solvatochromic effect is observed upon the addition of a C₆₀ solution in toluene to a water-acetone mixture.__________Translated from Kolloidnyi Zhurnal, Vol. 67, No. 4, 2005, pp. 575–576.Original Russian Text Copyright © 2005 by Tseluikin, Tolstova, Gun’kin, Pankst’yanov.     

Hydrogen generation from H<Subscript>2</Subscript>O/H<Subscript>2</Subscript>O<Subscript>2</Subscript>/MnWO<Subscript>4</Subscript> system

Hydrogen gas as a clear energy resource was found to be largely bubbled from a H₂O/H₂O₂/MnWO₄ system. MnWO₄ powder was fabricated by an aqueous reaction method. The powder was characterized with X-ray diffraction (XRD), transmission electron microscope (TEM), and X-ray photoelectron spectrometry (XPS). The efficiency of the hydrogen generation increases with an increase in initial pH in the appropriate range, H₂O₂ proportion, MnWO₄ proportion, and intensity of light resource. Calcining at 400 °C for 1 h can make the MnWO₄ powder synthesized by an aqueous reaction more effective for H₂ generation and more stable in higher initial pH. The MnWO₄ catalyst shows a long-term stability for photocatalytic H₂ generation. A mechanism was suggested for the hydrogen generation from the H₂O/H₂O₂/MnWO₄ system together with XPS analysis.     

Synthesis and structure of [UO<Subscript>2</Subscript>(C<Subscript>2</Subscript>O<Subscript>4</Subscript>){CONH<Subscript>2</Subscript>N(CH<Subscript>3</Subscript>)<Subscript>2</Subscript>}<Subscript>2</Subscript>]

The single crystals of [UO₂(C₂O₄){CONH₂N(CH₃)₂}₂] were synthesized and studied by X-ray diffraction. The crystals are monoclinic, a = 7.461(2) Å, b = 8.828(2) Å, c = 11.756(2) Å, β = 107.21(3)°, space group Pc, Z = 2, R = 2.94%. The structure comprises infinite chains [UO₂(C₂O₄){CONH₂N(CH₃)₂}₂] extended along [001] and corresponding to the AT¹¹M ₂ ¹ crystallochemical group (A = UO ₂ ²⁺ , T¹¹ = C₂O ₄ ^2? , M¹ = N,N-CONH₂N(CH₃)₂) of uranyl complexes. The chains are connected into a three-dimensional framework by hydrogen bonds involving the oxygen atoms of oxalate and uranyl ions and the N,N-dimethylcarbamide methyl groups.     

Preparation and characterization of the Ti/IrO<Subscript>2</Subscript>/WO<Subscript>3</Subscript> as supercapacitor electrode materials

WO₃ films have been prepared onto IrO₂-coated Ti substrate by electro-deposition, and as-deposited and annealed films have been characterized by using Raman spectroscopy. It was found that the asdeposited film consists of orthorhombic WO₃ · H₂O phase, which transforms to amorphous WO₃ by annealing at 250°C and to monoclinic phase by annealing at and above 350°C. All electrochemical experiments were carried on Ti/IrO₂/WO₃ annealed at 450°C. The open-circuit potential could change significantly due to the hydration of the coating film. However this process is fairly slow. Reproducible voltammograms could be obtained quickly, further revealing high electrochemical stability of the Ti/IrO₂/WO₃ electrode. And the shapes of CV show the approximate rectangular mirror image, showing the typical characteristic of capacitive behavior. The specific capacitance obtained at a scan rate of 50 mV s⁻¹ is 46 F g⁻¹.     

Preparation and photoelectrochemical performance of TiO<Subscript>2</Subscript>/Ag<Subscript>2</Subscript>Se interface composite film

Coupling TiO₂ with a narrow band gap semiconductor acting as the photosensitizer has attracted much attention in solar energy exploitation. In this work, the porous TiO₂ film was first formed on the conducting glass plate (CGP) substrate by the decomposition of polyethylene glycol (PEG) mixing in titanium hydroxide sol at 450°C. Then, the TiO₂/Ag²Se interface composite film was fabricated by interface reaction of AgNO₃ with NaSeSO₃ on the activated surface of porous TiO₂ film. The results of SEM and XRD analyses indicated that the porous TiO₂ layer was made up of the anatase crystal, and the Ag₂Se layer was made up of congregative small particles that have low-temperature α-phase structure. Due to its efficient charge separation for the photo-induced electron-hole pairs, the TiO₂/Ag₂Se interface composite film as-prepared has good photovoltaic property and high photocurrent response for visible light, which have been confirmed by the photoelectrochemical measurements.     

A comparative study of Ir/Ga<Subscript>2</Subscript>O<Subscript>3</Subscript>, Pt/Ga<Subscript>2</Subscript>O<Subscript>3</Subscript>, and Ru/Ga<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts in selective hydrogenation of crotonaldehyde

Catalytic performance of gallia-supported iridium catalysts in the reaction of selective hydrogenation of crotonaldehyde in the gas phase was studied and compared to that of platinum and ruthenium catalysts. The best catalytic properties in terms of the selectivity to crotyl alcohol are shown by 5 wt % Pt/α-Ga₂O₃ and 5 wt % Ir/α-Ga₂O₃ catalysts prepared from nonchlorine precursors: Pt(acac)₂ and Ir(acac)₃, but for the 5 wt % Pt/α-Ga₂O₃ a very high selectivity of 75% at the high conversion (ca. 60%) is observed. A high selectivity of galia-supported iridium and platinum catalysts was explained by the surface reducibility of gallium oxide leading to covering (decoration) of platinum and iridium by gallium suboxides and the promoting effect of gallium.     

Preparation and radioluminescent characteristics of Li<Subscript>2</Subscript>O-B<Subscript>2</Subscript>O<Subscript>3</Subscript>-P<Subscript>2</Subscript>O<Subscript>5</Subscript>-CaF<Subscript>2</Subscript> glasses doped with Ce(III) and Gd(III)

A method has been developed for the preparation of homogeneous moisture-resistant glasses with the composition Li₂O-B₂O₃-P₂O₅-CaF₂ : Ce³⁺-Gd³⁺. Energy transfer from Gd³⁺ to Ce³⁺ was noted in a study of the radioluminescence spectra of these samples using ²⁴¹Am as the excitation source (60 keV). The decay time of the Ce³⁺ radioluminescence in the glasses obtained was 20-25 ns.     

Specific heat on Sr<Subscript>2</Subscript>Nb<Subscript>2</Subscript>O<Subscript>7</Subscript> and Sr<Subscript>2</Subscript>Ta<Subscript>2</Subscript>O<Subscript>7</Subscript>

Summary Specific heats on the single crystals of Sr₂Nb₂O₇, Sr₂Ta₂O₇ and (Sr_1-xBa_x)₂Nb₂O₇ were measured in a wide temperature range of 2-600 K. Heat anomalies of a λ-type were observed at the incommensurate phase transition of T_INC (=495 K) on Sr₂Nb₂O₇ and at the super-lattice phase transition of T_SL (=443 K) on Sr₂Ta₂O₇; the transition enthalpies and the transition entropies were estimated. Furthermore, a small heat anomaly was observed at the low temperature ferroelectric phase transition of T_LOW (=95 K) on Sr₂Nb₂O₇. The transition temperature T_LOW decreases with increasing Ba content x and it vanishes for samples of x>2%.     

A First-Principles Calculation of Electronic Properties of LiNH<Subscript>2</Subscript> and NaNH<Subscript>2</Subscript>

Band spectra, densities of states, total and deformation densities of α-LiNH₂ and α-NaNH₂ are calculated from the first principles using the density functional method in the all-electron approximation. The upper valence band is formed mostly by nitrogen p-states with a small admixture of metal states, the lower conduction bands are formed by the states of all atoms in α-LiNH₂ and mainly by sodium and nitrogen states in α-NaNH₂. The bottom of the conduction band appears in both crystals in the center of the Brillouin zone. α-LiNH₂ exhibits indirect-gap transitions at the absorption edge and three valence band extrema at a short distance of ~0.15 eV from each other. The top of the valence band in α-NaNH₂ appears in the center of the Brillouin zone with the competing maximum at the lateral point at a distance of ~0.06 eV. The electron density distributions testify that polar covalent bonding occur inside the amide anion and ionic bonding occurs between the metal and the amide ion.     

Preparation and X-ray diffraction study of phosphate sulfates M<Subscript>2</Subscript>MgTi(SO<Subscript>4</Subscript>)(PO<Subscript>4</Subscript>)<Subscript>2</Subscript>

Phosphate sulfates M₂MgTi(SO₄)(PO₄)₂ (M = alkali metal) prepared by the sol–gel technique with ethanol as salting-out agent were characterized by differential thermal analysis, electron probe microanalysis, and X-ray phase analysis. The crystal structure of the compounds synthesized (M = Na, K) was refined by powder X-ray diffraction. The phase stability of the phosphate sulfates under heating was examined.     

Bimetallic Pt<Subscript>0.5</Subscript>Co<Subscript>0.5</Subscript>/SiO<Subscript>2</Subscript> Catalyst: Preparation,Structure, and Properties in Preferential Oxidation of Carbon Monoxide

The Pt_0.5Со_0.5/SiO₂ catalyst has been prepared by the decomposition of a [Pt(NH₃)₄][Co(C₂O₄)₂(H₂O)₂]. 2H₂O binary complex salt supported in the pores of SiO₂ pellets. It has been shown by a complex of physical and chemical methods that Pt_0.5Со_0.5/SiO₂ contains alloy nanoparticles with an average composition Pt0.5Co0.5. The catalytic properties of Pt_0.5Со_0.5/SiO₂ are studied in the preferential oxidation of СО in the reaction mixtures with various compositions. It was found that Pt_0.5Со_0.5/SiO₂ has a high selectivity and makes it possible to decrease the outlet concentration of CO to a level of <10 ppm, and the presence of СО₂ and/or Н₂О in the reaction mixture almost does not affect its catalytic properties. The structure of the catalyst is stable under the conditions of preferential CO oxidation.     

Study on chemisorption of H<Subscript>2</Subscript>, O<Subscript>2</Subscript>, CO and C<Subscript>2</Subscript>H<Subscript>4</Subscript>on Pt-Ag/SiO<Subscript>2</Subscript>catalysts by microcalorimetry and FTIR

Adsorption microcalorimetry has been employed to study the interaction of ethylene with the reduced and oxidized Pt-Ag/SiO₂catalysts with different Ag contents to elucidate the modified effect of Ag towards the hydrocarbon processing on platinum catalysts. In addition, microcalorimetric adsorption of H₂, O₂, CO and FTIR of CO adsorption were conducted to investigate the influence of Ag on the surface structure of Pt catalyst. It is found from the microcalorimetric results of H₂and O₂adsorption that the addition of Ag to Pt/SiO₂leads to the enrichment of Ag on the catalyst surface which decreases the size of Pt surface ensembles of Pt-Ag/SiO₂catalysts. The microcalorimetry and FTIR of CO adsorption indicates that there still exist sites for linear and bridged CO adsorption on the surface of platinum catalysts simultaneously although Ag was incorporated into Pt/SiO₂. The ethylene microcalorimetric results show that the decrease of ensemble size of Pt surface sites suppresses the formation of dissociative species (ethylidyne) upon the chemisorption of C₂H₄on Pt-Ag/SiO₂. The differential heat vs. uptake plots for C₂H₄adsorption on the oxygen-preadsorbed Pt/SiO₂and Pt-Ag/SiO₂catalysts suggest that the incorporation of Ag to Pt/SiO₂could decrease the ability for the oxidation of C₂H₄.     

Biosynthesis and Photocatalytic Properties of SnO<Subscript>2</Subscript> Nanoparticles Prepared Using Aqueous Extract of Cauliflower

This work reports the biosynthesis of Sn(OH)₂ using aqueous extract of fresh cauliflower (Brassica oleracea L. var. botrytis), and the subsequent preparation of SnO₂ nanoparticles at two different annealing temperatures of 300 and 450 °C for 2 h. The obtained SnO₂ nanoparticles were denoted as S1 and S2 for the samples prepared at 300 and 450 °C, respectively. XRD analysis identified rutile tetragonal phase of SnO₂ nanoparticles and TEM results gave a quasispherical and spherical morphologies for S1 and S2 respectively of the size range 3.62–6.34 nm. The optical properties were studied with UV–vis and photoluminescence (PL) spectroscopies, and the nanoparticles showed blue shift in their absorption edges. The observed emission peak in the PL spectra found around 419 nm is attributable to oxygen vacancies and defects. Photocatalytic activities of the nanoparticles (S1 and S2) were studied using methylene blue (MB) under ultraviolet light irradiation and the results reveal 91.89 and 88.23% degradation efficiency of MB by S1 and S2 respectively over a period of 180 min.