Mn-Sn-Sb/γ-Al2O3粒子电极对苯酚的降解特性

研制了复合氧化物负载型Mn-Sn-Sb/γ-Al₂O₃粒子电极并填充于主阴阳极之间,实现了三维电催化氧化反应,并采用XRD、SEM对粒子电极进行了表征.结果表明,该粒子电极对目标污染物苯酚显示了良好的电催化活性和稳定性,在相同反应条件下,不加粒子电极的二维电解时苯酚的降解率为55.6%,而三维电催化氧化过程中降解率为90.8%,大大提高了苯酚去除效果.研究苯酚降解的动力学规律表明,苯酚降解符合表观一级反应动力学规律.利用GC-MS分析了苯酚降解主要中间产物为异丁酸、丙二酸、对苯醌、丁烯酸、乙二酸、顺丁烯二酸、丁二酸、邻苯二酚、对苯二酚及间苯二酚等,并据此推测了苯酚电催化氧化的可能反应途径.     

Effects of porosity on the electrochemical oxidation performance of Ti4O7 electrode materials

Ti₄O₇ is a kind of conductive ceramic material with a high electrical conductivity and excellent electrochemical performance, rendering it a potential candidate for electrode applications. Here, for the first time, we report the successful preparation of Ti₄O₇ electrodes with different porosities by adding a pore-forming agent. The results showed that the as-prepared Ti₄O₇ electrodes contained both mesoporous and macroporous structures. In addition, with an increase in the porosity of the electrodes, the electrochemical oxidation degradation of high-concentration methyl orange (MO) solution first increased, until reaching a critical point, and then decreased. The Ti₄O₇ electrode with a porosity of 34.9% and an electrical conductivity of 336.1 S cm^-1 exhibited the highest electrochemical oxidation ability. The electrochemical oxidation rate constants for MO and chemical oxygen demand (COD) of the porous Ti₄O₇ electrode were 1.7 times those of the dense Ti₄O₇ electrode. Compared to commercial stainless steel, graphite, and Ti/RuO₂ electrodes, the Ti₄O₇ porous electrode showed superior electrochemical oxidation performance under the same experimental conditions. The result of this study provide new directions for the application of Ti₄O₇ electrode materials.     

Deactivation and regeneration of Pt anodes for the electro-oxidation of phenol

Electro-oxidation tests with different electrolytes (Na₂SO₄, NaCl, H₂SO₄) and anode types (Pt, Ti lined with Ir and Ta oxides, PbO₂, activated carbon) were performed on aqueous solutions containing phenol to assess the mechanism and nature of electrode deactivation phenomena. For the Pt electrode, the nature of the electro-deposited organic species was investigated by ATR-FTIR and FESEM-EDS analyses, which showed adsorption of intermediate oxidation products (e.g. benzoquinone, hydroquinone) is likely responsible for the early deactivation stages. Conversely, in the longer term, formation of polymeric films is promoted. Potentiostatic tests showed that anode regeneration can be achieved by anodic polarisation above 1.1 V (vs Hg/Hg₂SO₄). This reactivation was found to be easier in the presence of significant amounts of chloride ions. Conversely, the deactivated state is maintained for the Ti/IrO₂/Ta₂O₅ electrode even though anodic polarisation at high positive potentials is applied. Cyclic voltammetric curves on PbO₂ electrodes did not provide satisfactory results as the intensity of the lead-dioxide reduction peak was so high that peaks for phenol oxidation were hardly detectable. Finally, the activated carbon based electrode was found to be promising as it enables simultaneous adsorption of the organic pollutant and oxidation of the pollutant itself to constitute a sort of self-regenerating adsorber unit.     

Performance of sol–gel Titanium Mixed Metal Oxide electrodes for electro-catalytic oxidation of phenol

Mixed metal oxides SnO₂–RuO₂–IrO₂, Ta₂O₅–IrO₂ and RhO₂–IrO₂ were immobilised on a Ti substrate using sol–gel techniques. The Ti mixed metal oxides were characterized in terms of morphology using scanning electron microscopy. Cyclic voltammetric responses of phenol at Ti/SnO₂–RuO₂–IrO₂, Ti/Ta₂O₅–IrO₂ and Ti/RhO₂–IrO₂ electrodes were evaluated and showed significantly low potentials for Ti/Ta₂O₅–IrO₂ (+100 mV), Ti/SnO₂–RuO₂–IrO₂ (+200 mV) and Ti/RhO₂–IrO₂ (−100 mV). The degradation of phenol in aqueous solution and its intermediates were investigated by bulk electrolysis and quantitatively assessed by HPLC analysis to elucidate the decomposition pathways and to develop a kinetic model for the electro-catalytic oxidation of phenol over Ti mixed metal oxides. Ring compounds, benzoquinone/hydroquinone, catechol, and short chain organics, carboxylic acids, have been identified as intermediate products for the electro-catalytic oxidation of phenol. Fundamental kinetic data were obtained for the conversion of phenol at these electrodes and was found to proceed in accordance with the pseudo-first-order kinetics with respect to the phenol concentration.     

Electrochemical degradation of 2,4-dichlorophenol on a palladium modified gas-diffusion electrode

Pd/C catalyst was prepared by hydrogen reduction method and used for the Pd/C gas-diffusion electrode. It was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV) techniques. The electrochemical degradation of 2,4-dichlorophenol was investigated in a diaphragm electrolysis system, feeding firstly with hydrogen gas then with air, using the Pd/C gas-diffusion electrode and the carbon/polytetrafluoroethylene (C/PTFE) gas-diffusion electrode as a cathode, respectively. The results indicated that the self-made Pd/C gas-diffusion cathode can not only reductively dechlorinate 2,4-dichlorophenols by feeding hydrogen gas, but also accelerate the two-electron reduction of O₂ to hydrogen peroxide (H₂O₂) by feeding air. Therefore, both the removal efficiency and the dechlorination degree of 2,4-dichlorophenol reached about 100% after 80 min, and the average removal efficiency of 2,4-dichlorophenol in terms of total organic carbon (TOC) exceeded 76% after 160 min by using Pd/C gas-diffusion cathode, which were better than that of the C/PTFE gas-diffusion cathode. The analysis of high-performance liquid chromatography (HPLC) identified that 4-chlorophenol, 2-chlorophenol, and phenol were the dechlorination products, and hydroquinone, benzoquinone, maleic, fumaric, crylic, malonic, oxalic, acetic and formic acids were the main oxidation intermediates. A reaction scheme involving all these intermediates was proposed.     

A novel catalyst for clean production of diphenols—ferric trisacetylacetonate/MCM-41

Ferric trisacetylacetonate has been deposited within the zeolite MCM-41 and the product characterized by XRD and IR. In water at pH 7 it catalyzes the oxidation of phenol by H₂O₂, giving 58% conversion in 1 h at 50°C: products are catechol (66%), hydroquinone (27%) and benzoquinone (7%). Other oxidants and solvents are much less effective. UV-VIS spectra suggest a radical substitution mechanism, and a pollution-free process for phenol hydroxylation is now possible. ©1997 SCI     

Ge-doped Li4Ti5-xGexO12 (x = 0.05) as a fast-charging,long-life bi-functional anode material for lithium- and sodium-ion batteries

We explored the doping effect of Ge⁴⁺ on the Li₄Ti_5-xGe_xO₁₂ (x = 0.0 and 0.05) anode material by looking at its electrochemical performance in both Li- and Na-ion batteries. Combined analysis using Rietveld refinement of high-resolution powder diffraction (HRPD) and transmission electron microscopy (TEM) unambiguously identified homogeneous Ge doping into the 16c octahedral Ti site of the Li₄Ti₅O₁₂ (LTO) cubic spinel structure. This Ge doping leads to a much-reduced particle size, slightly expanded lattice and increased electrical conductivity due to the increased Ti³⁺ to Ti⁴⁺ ratio, these results were verified by HRPD, scanning electron microscopy (SEM), 4-point probe and x-ray photoelectron spectroscopy (XPS) analysis. The Li₄Ti_4.95Ge_0.05O₁₂ (Ge0.05-LTO) electrode shows much-improved capacity, high-rate capability and excellent cycling stability in a Li-half cell compared with an un-doped LTO electrode. This performance improvement is due to the reduced Li⁺ diffusion path and faster Li⁺ insertion/extraction kinetics that originate from Ge doping. In addition to these results, when tested as an anode for SIBs, the Ge0.05-LTO electrode exhibits enhanced capacity and cycling stability compared to un-doped LTO electrode, demonstrating its bi-functional, advantageous features in both LIB and SIB systems.     

Preparation of micro-dot electrodes of LiCoO2 and Li4Ti5O12 for lithium micro-batteries

Fabrications of micro-dot electrodes of LiCoO₂ and Li₄Ti₅O₁₂ on Au substrates were demonstrated using a sol-gel process combined with a micro-injection technology. A typical size of prepared dots was about 100 μm in diameter, and the dot population on the substrate was 2400 dots cm⁻². The prepared LiCoO₂ and Li₄Ti₅O₁₂ micro-dot electrodes were characterized with scanning electron microscopy, X-ray diffraction, micro-Raman spectroscopy, and cyclic voltammetry. The prepared LiCoO₂ and Li₄Ti₅O₁₂ micro-dot electrodes were evaluated in an organic electrolyte as cathode and anode for lithium micro-battery, respectively. The LiCoO₂ micro-dot electrode exhibited reversible electrochemical behavior in a potential range from 3.8 to 4.2 V versus Li/Li⁺, and the Li₄Ti₅O₁₂ micro-dot electrode showed sharp redox peaks at 1.5 V.     

Effect of heat treatment on electrochemical characteristics of spinel lithium titanium oxide

Spinel structured LTO (lithium titanium oxide), Li₄Ti₅O₁₂, materials have gained renewed interest in electrodes for lithium-ion batteries. Powder precursors were mixed by HEBM (high energy-ball mill) and Li₄Ti₅O₁₂ was formed by calcinations at high temperature. The influence of excess Li on the structural characteristics of lithium titanium oxide was investigated. According to the XRD and SEM analysis, uniformly distributed Li₄Ti₅O₁₂ particles were synthesized. Li₄Ti₅O₁₂ had different characteristics due to the precursor sizes and the heat treatment temperatures. LTO from micro TiO₂ showed the highest discharge capacity at 750 °C for 12 h. LTO from nano TiO₂ showed the highest discharge capacity at 700 °C for 12 h. Lithium-ion battery with Li₄Ti₅O₁₂ anode and lithium metal cathode showed the capacity of 170 mAh/g at 1.0–3.0 V.     

Structural and electronic properties of Ce-doped Ti4O7 based on experiments and first-principles calculations

A series of Ti₄O₇ powders with different Ce-cation doping concentrations were successfully prepared through a new strategy combining the wet chemical method and hydrogen thermal reduction. It is shown that Ce, entering the lattice of Ti₄O₇ during the reduction process, only occurs in the form of Ce³⁺, and the solubility of Ce is equal to 8.93 at.%. Furthermore, the electrical conductivity of Ce-doped Ti₄O₇ powders was tested for the first time and theoretically explained by the first-principles calculations. It was revealed that Ce provides a negative effect on the electrical conductivity of Ti₄O₇ powders, which is due to the decrease in the number of electronic states near the Fermi energy level caused by the introduction of Ce.     

Sintering behavior of Y-doped BaZrO3 refractory with TiO2 additive and effects of its dissolution on titanium melts

In this study, the sintering behavior of Y-doped BaZrO₃ with TiO₂ additive and effects of its dissolution on titanium melts were investigated. In order to overcome the difficulty of Y-doped BaZrO₃ sintering performance, the 0-5 wt% TiO₂ was added into Y-doped BaZrO₃ and its densification was investigated by density analyzer, scanning electron microscope (SEM) and X-ray diffraction (XRD). Thereafter, the interface reaction between two crucibles (without and with 2 wt% TiO₂) and titanium alloys, the thermodynamics and kinetics of dissolution reaction were also investigated. The results showed that Y-doped BaZrO₃ was rarely dense without TiO₂ additive and its relative density was just 88%, while after doping 2 wt% TiO₂, the relative density was more than 97%. However, with the excessive TiO₂(>2 wt%) doping, the secondary phase was observed by SEM and XRD. After melting titanium-rich alloys (Ti₂Ni, 66 mol% Ti) by Y-doped BaZrO₃ crucibles without and with 2% TiO₂ additive, the erosion layer of the two crucibles was approximately 4000 and 1700 μm, respectively. It was also found that the dissolved reaction rate was related to the density and grain size of Y-doped BaZrO₃ ceramic; the higher density and larger grain size ceramics can effectively prevent the crucible from being eroded by Ti₂Ni melt.     

Electrosynthesis of benzoquinone from phenol on α and β surfaces of PbO2

Electrosynthesis of benzoquinone from phenol was investigated in acetonitrile-water mixtures on α-PbO₂ and β-PbO₂ electrodes. The influence of water concentration, electrolysis potential, initial phenol concentration and temperature on benzoquinone production was also studied. Different electrocatalytic activities of α and β structures of PbO₂ were determined.     

Electrochemical oxidation of 4-chlorophenol and its by-products using Ti/Ru<Subscript>0.3</Subscript>M<Subscript>0.7</Subscript>O<Subscript>2</Subscript> (M = Ti or Sn) anodes: preparation route versus degradation efficiency

The electrochemical degradation of 4-chlorophenol and its main by-products was investigated in acid medium using binary oxides electrodes of nominal composition Ti/Ru_0.3Ti_0.7O₂ and Ti/Ru_0.3Sn_0.7O₂ prepared by thermal decomposition through two different routes: inorganic precursors dissolved in isopropanol and polymeric precursors (PPM). The aim of this study was to investigate the influence of both the composition and preparation methodology of these electrodes in the electrooxidation of the organic pollutants 4-chlorophenol and its by-products. Electrolyses were carried out using a filter press-type flow cell and monitored by high performance liquid chromatography (HPLC), total organic carbon (TOC), and chloride analyses. Besides CO₂, the by-products formed in the reactions were 1,4-benzoquinone, 4-chlorocatechol, and hydroquinone, as well as oxalic, maleic, malic, malonic, and succinic acids. The electrocatalytic efficiency with respect to the degradation of by-products was evaluated through the electrooxidation of 1,4-benzoquinone and oxalic acid (OA). The anodes investigated in this work are very promising for the degradation of pollutants because of their excellent efficiency concerning the consumption of 4-chlorophenol and its by-products, although the mineralization of the starting material is not complete. The cleavage of the aromatic ring occurs preferentially in the case of electrodes prepared by decomposition of inorganic precursors due to their larger electrochemically active area and electrocatalytic activity for oxygen evolution reaction (OER). However, OA oxidation is favored on Ti/Ru_0.3Sn_0.7O₂ prepared through decomposition of PPM.     

Thermodynamic parameters of activation for photodegradation of phenolics

The photocatalytic degradation of three phenolics namely phenol, 4-chlorophenol and 4-nitrophenol were carried out in aerated aqueous suspension of TiO₂ irradiated by ultraviolet light. The influence of temperature at optimized pH and TiO₂ concentration was studied. The degradation kinetics were somewhat accelerated by increase in temperature in the range 25–45 °C and apparent activation energy was calculated to be 9.68–21.44 kJ mol^?1. Thermodynamic parameters of activation were also assessed for the degradation process. Formation of acidic species results in decrease in pH of solution. The appearance and the evolution of main intermediate species like hydroquinone, benzoquinone and catechol during the degradation process were computed by UV–vis spectral analysis.     

All-solid-state lithium battery with a three-dimensionally ordered Li1.5Al0.5Ti1.5(PO4)3 electrode

To fabricate all-solid-state Li batteries using three-dimensionally ordered macroporous Li_1.5Al_0.5Ti_1.5(PO₄)₃ (3DOM LATP) electrodes, the compatibilities of two anode materials (Li₄Mn₅O₁₂ and Li₄Ti₅O₁₂) with a LATP solid electrolyte were tested. Pure Li₄Ti₅O₁₂ with high crystallinity was not obtained because of the formation of a TiO₂ impurity phase. Li₄Mn₅O₁₂ with high crystallinity was produced without an impurity phase, suggesting that Li₄Mn₅O₁₂ is a better anode material for the LATP system. A Li₄Mn₅O₁₂/3DOM LATP composite anode was fabricated by the colloidal crystal templating method and a sol-gel process. Reversible Li insertion into the fabricated Li₄Mn₅O₁₂/3DOM LATP anode was observed, and its discharge capacity was measured to be 27 mA h g⁻¹. An all-solid-state battery composed of LiMn₂O₄/3DOM LATP cathode, Li₄Mn₅O₁₂/3DOM LATP anode, and a polymer electrolyte was fabricated and shown to operate successfully. It had a potential plateau that corresponds to the potential difference expected from the intrinsic redox potentials of LiMn₂O₄ and Li₄Mn₅O₁₂. The discharge capacity of the all-solid-state battery was 480 μA h cm⁻².     

Electrical properties of niobium doped Bi4Ti3O12-SrBi4Ti4O15 intergrowth ferroelectrics

Nb-doped Bi₄Ti₃O₁₂-SrBi₄Ti₄O₁₅ intergrowth ceramics have been prepared by modified oxalate route. XRD phase analysis confirmed the formation of single phase compound. Nb-doping does not affect the basic crystal structure of the intergrowth. SEM micrographs showed that the grain size of the ceramics decreases with Nb-doping. The temperature dependence of dielectric constant and losses was investigated in the temperature range 30–800 °C and frequency range 1 kHz–1 MHz. With Nb-doping, the T_c of the ferroelectrics reduces and peak permittivity increases. Doping also introduces small relaxor behavior in the ferroelectrics. The dc conductivity of the ceramics decreases with doping. The remnant polarization (P_r) of the intergrowth ferroelectrics is increased with Nb doping.     

Photocatalyzed Degradation of Phenol, 2,4-Dichlorophenol,Phenoxyacetic Acid and 2,4-Dichlorophenoxyacetic Acid over SupportedTiO2 in a Flow System

The photodegradation of phenol, 2,4-dichlorophenol, phenoxyacetic acid and 2,4-dichlorophenoxyacetic acid using TiO₂ as photocatalyst is investigated. The photodegradations of these compounds have been conducted in a continuous mode by means of a flow system, in which TiO₂ remains fixed onto glass pearls. The use of this system gives high yields of degradation for the chemicals tested, except for 2,4-dichlorophenol for which a slow dechlorination process is observed. The rate of photodegradation depends on the pH of the solution, the point of zero charge of TiO₂ and the pK_a of the chemicals being the key parameters. The main aromatic intermediates detected have been hydroquinone,paraquinone and hydrohydroquinone during phenol degradation; phenol and hydroquinone during phenoxyacetic acid degradation; chlorohydroquinone and chlorophenol during 2,4-dichlorophenol degradation; and dichlorophenol during 2,4-dichlorophenoxyacetic acid degradation. Finally, some long term irradiations with phenol as model compound have been performed, showing high degrees of photodegradation. It has been observed that only a periodic evacuation of the effluent out of the reactor is needed to sustain high percentages of photodegradation.     

Voltametric behaviour of Ti n O2n−1 ceramic electrodes close to the hydrogen evolution reaction

Voltammetric behaviour close to the hydrogen evolution reaction has been studied on metallic conducting oxides from Ti _n O_2n–1 series with n = 4–6. The Ti₄O₇, Ti₅O₉ and Ti₆O₁₁ ceramic electrodes were prepared by the reduction of TiO₂ compacts with hydrogen. The current-voltage curves (i, E) were obtained by the potentiodynamic method in aqueous solutions. The electrochemical reaction which occurs in the cathodic potential region is discussed in terms of proton insertion into the Ti _n O_2n–1 structure. The influence of the porosity of the ceramic electrodes on the electrochemical reaction taking place in this potential region was examined using electrodes of different pore size distributions (different values of roughness factor, r). The influence of the degree of reduction of titanium oxide (n in Ti _n O_2n–1) on the electrolytic activity for the hydrogen evolution reaction on these oxides was examined.     

Preparation of Ti/SnO2-Sb2O4 photoanode by electrodeposition and dip coating for PEC oxidations

Thin films of antimony-doped SnO₂ on titanium substrate with a doping range of 1.5-8 mol% were prepared by an electrodeposition and dip coating method. The prepared Ti/SnO₂-Sb₂O₄ thin films were tested as a photoanode in the photoelectrocatalytic(PEC) experiments to degrade phenol in aqueous solution in order to evaluate their PEC performance. The photocatalytic (PC), electrocatalytic (EC) and PEC activity of Ti/SnO₂-Sb₂O₄ thin films was compared in the degradation processes. And the effect of annealing temperature on their PEC activity was also investigated. The experimental results confirmed that the Sb-doped Ti/SnO₂ thin films enhanced the phenol degradation and the Ti/SnO₂-Sb₂O₄ film containing 6 mol% of Sb calcinated at 450 °C achieved the best performance for phenol degradation. The degradation experiments also demonstrated that the Ti/SnO₂-Sb₂O₄ film achieved faster degradation of phenol in the PEC process than in the PC and EC processes. Compared with Ti/TiO₂ and Ti/SnO₂ photoanodes, the Ti/SnO₂-Sb₂O₄ photoanode showed higher activity.     

含酚模拟废水的电催化降解

研究了含酚模拟废水 (10 0～ 80 0mg·L^-1)在经氟树脂改性的 β -PbO₂ 电极上的电催化降解 .考察了废水中盐含量、电压、pH值、苯酚初始浓度对废水COD去除的影响 .在温度 2 5℃、电压 7.0V、K₂ SO₄ 含量为1.0 g·L^-1、pH值为 2 .0时 ,模拟苯酚 (10 0mg·L^-1)废水经 2 5min处理 ,COD降至 6 0mg·L^-1以下 ,挥发酚完全消失 .该方法用于处理含酚浓度大 ,酸性高且有一定盐含量的废水 ,可以不经稀释或中和调节等预处理而直接处理 ,具有很好的应用前景 .苯酚降解的主要产物为苯醌、丁烯二酸和草酸 ,最终产物为二氧化碳 ,因此该工艺可用于有机物污染最小化处理和处理水的回用 .COD的去除符合表观拟一级反应动力学