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1.
This study investigated the effect of a specific adsorption ion, copper (II) ion, on the kinetics of the charge transfer reaction at a LiMn2O4 thin film electrode/aqueous solution (1 mol dm−3 LiNO3) interface. The zeta potential of LiMn2O4 particles showed a negative value in 1 × 10−2 mol dm−3 LiNO3 aqueous solution, while it was measured as positive in the presence of 1 × 10−2 mol dm−3 Cu(NO3)2 in the solution. The presence of copper (II) ions in the solution increased the charge transfer resistance, and CV measurement revealed that the lithium insertion/extraction reaction was retarded by the presence of small amount of copper (II) ions. The activation energy for the charge transfer reaction in the solution with Cu(NO3)2 was estimated to be 35 kJ mol−1, which was ca. 10 kJ mol−1 larger than that observed in the solution without Cu(NO3)2. These results suggest that the interaction between the lithium ion and electrode surface is a factor in the kinetics of charge transfer reaction. 相似文献
2.
J. Ribeiro F.L.S. Purgato k.B. Kokoh J.-M. Léger A.R. de Andrade 《Electrochimica acta》2008,53(27):7845-7851
The influence of the preparation method on the performance of RuO2-Ta2O5 electrodes was evaluated toward the ethanol oxidation reaction (EOR). Freshly prepared RuO2-Ta2O5 thin films containing between 30 and 80 at.% Ru were prepared by two different methods: the modified Pechini-Adams method (DPP) and standard thermal decomposition (STD). Electrochemical investigation of the electrode containing RuO2-Ta2O5 thin films was conducted as a function of electrode composition in a 0.5-mol dm−3 H2SO4 solution, in the presence and absence of ethanol and its derivants (acetaldehyde and acetic acid).At a low ethanol concentration (5 mmol dm−3), ethanol oxidation leads to high yields of acetic acid and CO2. On the other hand, an increase in ethanol concentration (15-1000 mmol dm−3) favors acetaldehyde formation, so acetic acid and CO2 production is hindered, in this case.Electrodes prepared by DPP provide higher current efficiency than STD electrodes for all the investigated ethanol concentrations. This may be explained by the increase in electrode area obtained with the DPP preparation method compared with STD. 相似文献
3.
Electropolishing of NiTi shape memory alloys in methanolic H2SO4 总被引:2,自引:0,他引:2
The electropolishing of NiTi shape memory alloys was surveyed electrochemically. Anodic polarization of NiTi up to 8 V was performed in various aqueous and methanolic H2SO4 solutions. The passivity could be overcome in methanolic solutions with 0.1 mol dm−3≤CH2SO4≤7 mol dm−3. The dissolution kinetics was studied in dependence of the polarization potential, the H2SO4-concentration, the water concentration and the temperature. For lower concentrations of sulfuric acids (CH2SO4≤0.3 mol dm−3) electropolishing conditions were not observed for potentials up to 8 V. The dissolution remained under Ohmic control. In the concentration range from 1 to 7 mol dm−3 a potential independent limiting current was registered depending linearly on the logarithm of concentration. The best results were obtained with a 3 mol dm−3 methanolic sulfuric acid at 263 K which yielded an electropolishing current of 500 A m−2 at a potential of 8 V. Surface roughness as well as current efficiency showed an optimum under these conditions. 相似文献
4.
In this work, SiO2/Sb2O3 prepared by the sol-gel processing method, having a specific surface area, SBET, 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. 相似文献
5.
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.%. 相似文献
6.
Cobalt aluminate (CoAl2O4) thin films were grown in a low-pressure hot wall metal organic chemical vapour deposition (MOCVD) reactor on Si(1 0 0) and quartz substrates with a total pressure of 2 Torr using bis(η5-cyclopentadienyl)Co(II) [Co(η5-C5H5)2] and aluminium dimethylisopropoxide [AlMe2(OiPr)] as precursors at 500 and 900 °C. Films showed a dark-brown and dark-green colouration, respectively, and after an overnight heat treatment in air at 1200 °C, they turned blue. Film microstructure, composition and morphology were investigated in detail by X-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS), scanning electron microscopy (SEM) and secondary ion mass spectrometry (SIMS) analyses. Films were polycrystalline and the UV-vis spectra showed three electronic transitions allowed by the spin (540-630 nm range) characteristic of Co(II) ions with 3d7 configuration in tetrahedral coordination. SEM micrographs of the heat-treated CoAl2O4 samples revealed the presence of agglomerated crystallites with a highly porous structure. 相似文献
7.
In this paper, we studied the development of a selective lithium ion sensor constituted of a carbon paste electrode modified (CPEM) with an aluminum-doped spinel-type manganese oxide (Li1.05Al0.02Mn1.98O4) for investigating the influence of a doping ion in the sensor response. Experimental parameters, such as influence of the lithium concentration in the activation of the sensor by cyclic voltammetry, pH of the carrier solution and selectivity for Li+ against other alkali and alkaline-earth ions were investigated. The sensor response to lithium ions was linear in the concentration range 5.62 × 10−5 to 1.62 × 10−3 mol L−1 with a slope 100.1 mV/decade over a wide pH 10 (Tris buffer) and detection limit of 2.75 × 10−5 mol L−1, without interference of other alkali and alkaline-earth metals, demonstrating that the Al3+ doping increases the structure stability and improves the potentiometric response and sensitivity of the sensor. The super-Nernstian response of the sensor in pH 10 can be explained by mixed potential arising from two equilibria (redox and ion-exchange) in the spinel-type manganese oxide. 相似文献
8.
Electrochemical degradation of azo dye C.I. Reactive Red 195 by anodic oxidation on Ti/SnO2-Sb/PbO2 electrodes 总被引:1,自引:0,他引:1
This study investigated the electrochemical degradation of C.I. Reactive Red 195 (RR195) in aqueous solution on a Ti/SnO2-Sb/PbO2 electrode. The influence of operating variables on the mineralization efficiency was studied as a function of the current density, the initial pH, the initial concentration of the dye and the addition of NaCl. The efficiency of RR195 mineralization decreased with increased initial concentration, from 100 mg L−1 to 400 mg L−1. The current density had both a positive and a negative effect on degradation rates, and no significant effect of initial pH on RR195 mineralization was observed. Measurement of absorbance was used to discriminate the effect of NaCl in the electro-oxidation process. We found that the decolouring efficiency increased whereas the mineralization efficiency decreased with the increasing concentration of NaCl. The intermediates formed during the degradation were detected by gas chromatography-mass spectrometry, and the major aromatic intermediates identified were 1-(3,6,8-trihydroxy-1-naphthyl)urea, nitrobenzene, benzo-1,4-quinone, (3,6,8-trihydroxy-1-naphthyl)carbamic acid and phthalic acid. Quantitative measurement of organic and inorganic ions was done by ion chromatography. On the basis of the reaction products identified, a possible degradation pathway for the anodic oxidation of RR195 in aqueous solution is proposed. 相似文献
9.
A systematic investigation of the influence of Ti/[IrO2-Nb2O5] electrode composition ([IrO2]=40, 45 and 50 mol%) on electrochemical ozone production (EOP), was conducted in 3.0 mol dm−3 H2SO4 in the presence and absence of 0.03 mol dm−3 KPF6. “In situ” characterisation revealed all oxide layer presented similar structures, except for the 50 mol% IrO2 nominal composition which showed a higher porosity/roughness. The introduction of KPF6 in the electrolyte resulted in an inhibition of the oxygen evolution reaction (OER) at high current densities, improving ozone generation efficiency at i > 0.4 A cm−2, while reducing overpotential for OER. When normalised for the area, the ozone current efficiency presented a good performance of the system. However, improvement of the electrode service life is necessary in order to support the drastic conditions observed during EOP. 相似文献
10.
Solid state glass electrolyte, xLi2O-(1 − x)(yB2O3-(1 − y)P2O5) glasses were prepared with wide range of composition, i.e. x = 0.35 - 0.5 and y = 0.17 - 0.67. This material system is one of the parent compositions for chemically and electrochemically stable solid-state electrolyte applicable to thin film battery. Lithium ion conductivity of Li2O-B2O3-P2O5 glasses was studied in the correlation to the structural variation of glass network by using FTIR and Raman spectroscopy. The measured ionic conductivity of the electrolyte at room temperature increased with x and y. The maximum conductivity of this glass system was 1.6 × 10−7 Ω−1 cm−1 for 0.45Li2O-0.275B2O3-0.275P2O5 at room temperature. It was shown that the addition of P2O5 reduces the tendency of devitrification and increases the maximum amount of Li2O added into glass former without devitrification. As Li2O and B2O3 contents increased, the conductivity of glass electrolyte increased due to the increase of three-coordinated [BO3] with a non-bridging oxygen (NBO). 相似文献
11.
12.
The modification of activated carbon fibres prepared from a commercial textile acrylic fibre into materials with monolithic shape using phenolic resin as binder was studied. The molecular sieving properties for the gas separations CO2/CH4 and O2/N2 were evaluated from the gas uptake volume and selectivity at 100 s contact time taken from the kinetic adsorption curves of the individual gases. The pseudo-first order rate constant was also determined by the application of the LDF model. The samples produced show high CO2 and O2 rates of adsorption, in the range 3-35 × 10−3 s−1, and in most cases null or very low adsorption of CH4 and N2 which make them very promising samples to use in PSA systems, or similar. Although the selectivity was very high, the adsorption capacity was low in certain cases. However, the gas uptake in two samples reached 23 cm3 g−1 for CO2 and 5 cm3 g−1 for O2, which can be considered very good. The materials were heat-treated using a microwave furnace, which is a novel and more economic method, when compared with conventional furnaces, to improve the molecular sieves properties. 相似文献
13.
Graphene nanosheet (GNS)/Co3O4 composite has been rapidly synthesized by microwave-assisted method. Field emission scanning electron microscopy and transmission electron microscopy observation reveals the homogeneous distribution of Co3O4 nanoparticles (3-5 nm in size) on graphene sheets. Electrochemical properties are characterized by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. A maximum specific capacitance of 243.2 F g−1 has been obtained at a scan rate of 10 mV s−1 in 6 M KOH aqueous solution for GNS/Co3O4 composite. Furthermore, the composite exhibits excellent long cycle life along with ∼95.6% specific capacitance retained after 2000 cycle tests. 相似文献
14.
Mohammad A. Behnajady Behrouz Vahid Nasser Modirshahla Mohammad Shokri 《Desalination》2009,249(1):99-103
The kinetics of decolorization of Malachite Green (MG) as a model cationic dye from textile industry, by US/UV/H2O2 process, was investigated with nonlinear regression analysis. The experimental results indicated that the decolorization kinetics of MG in this process fit well by pseudo-first order kinetics. With nonlinear regression analysis a model was developed for pseudo-first order constant (kap) as a function of operational parameters such as initial concentrations of H2O2 (25-600 mg l− 1) and MG (1.82-9.87 mg l− 1), temperature (294-307 K) and power density (0.049-0.16 W ml− 1) as following:
15.
A three-dimensional ordered macroporous (3DOM) cobalt ferrite (CoFe2O4) was prepared using polystyrene (PS) colloidal crystal template. The scanning electron microscopy (SEM) and the transmission electron microscopy (TEM) micrographs showed that the as-prepared CoFe2O4 material had a typical 3DOM structure, which was constructed with about 130 nm-sized macropores and 10-20 nm-sized walls. The obtained CoFe2O4 material had a specific surface area of 66.67 m2 g−1, and could deliver a relatively high capacity of 702 mAh g−1 (about double that of graphite) at a current density of 0.2 mA cm−2 after 30 cycles. Owing to the 3DOM nanoarchitecture, the as-prepared CoFe2O4 electrode exhibited a good rate performance. The results suggest a promising application of the 3DOM CoFe2O4 as anode material for lithium ion batteries. 相似文献
16.
Some polyanionic compounds, e.g. TiP2O7 and LiTi2(PO4)3 with 3D framework structure were proposed to be used as anodes of lithium ion battery with aqueous electrolyte. The cyclic voltammetry properties TiP2O7 and LiTi2(PO4)3 suggested that Li-ion de/intercalation reaction can occur without serious hydrogen evolution in 5 M LiNO3 aqueous solution. The TiP2O7 and LiTi2(PO4)3 give capacities of about 80 mAh/g between potentials of −0.50 V and 0 V (versus SHE) and 90 mAh/g between −0.65 V and −0.10 V (versus SHE), respectively. A test cell consisting of TiP2O7/5 M LiNO3/LiMn2O4 delivers approximately 42 mAh/g (weight of cathode and anode) at average voltage of 1.40 V, and LiTi2(PO4)3/5 M LiNO3/LiMn2O4 delivers approximately 45 mAh/g at average voltage of 1.50 V. Both as-assembled cells suffered from short cycle life. The capacity fading may be related to deterioration of anode material. 相似文献
17.
Layered metastable lithium manganese oxides, Li2/3[Ni1/3−xMn2/3−yMx+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-Na2/3[Ni1/3−xMn2/3−yMx+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 Ni1/3−xMn2/3−yMx+yO2 slab. It was found that the stacking sequence and electrochemical performance of the Li cells containing T#2-Li2/3[Ni1/3Mn2/3]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. 相似文献
18.
O. YahiaouiN. Abdi N. Drouiche N. GhaffourA. Pauss N. Mameri 《Chemical Engineering and Processing: Process Intensification》2011,50(1):37-41
The main purpose of this study was to investigate the removal of the chemical oxygen demand (COD) from olive mill wastewater (OMW) by the combination of ultrafiltration with electrocoagulation process. Ultrafiltration process equipped with CERAVER membrane was used as pre-treatment for electrochemical process. The obtained permeate from the ultrafiltration process allowed COD removal efficiency of about 96% from OMW. Obtained permeate with an average COD of about 1.1 g dm−3 was treated by electrochemical reactor equipped with a reactor with bipolar iron plate electrodes. The effect of the experimental parameters such as current density, pH, surface electrode/reactor volume ratio and NaCl concentration on COD removal was assessed. The results showed that the optimum COD removal rate was obtained at a current density of 93.3 A m−2 and pH ranging from 4.5 to 6.5. At the optimum operational parameters for the experiments, electrocoagulation process could reduce COD from 1.1 g dm−3 to 78 mg dm−3, allowing direct discharge of the treated OMW as that meets the Algerian wastewater discharge standards (<125 mg dm−3). 相似文献
19.
Au nanoparticles (AuNPs) are good quenchers once they closely contact with luminophore. Here we reported a simple approach to obtain enhanced electrogenerated chemiluminescence (ECL) behavior based on Au/CdS nanocomposite films by adjusting the amount of AuNPs in the nanocomposite. The maximum enhancement factor of about 4 was obtained at an indium tin oxide (ITO) electrode in the presence of co-reactant H2O2. The mechanism of this enhancement was discussed in detail. The strong ECL emission from Au/CdS nanocomposites film was exploited to determine H2O2. The resulting ECL biosensors showed a linear response to the concentration of H2O2 ranging from 1.0 × 10−8 to 6.6 × 10−4 mol L−1 with a detection limit of 5 nmol L−1 (S/N = 3) and good stability and reproducibility. 相似文献
20.
Xiaozhen Zhang 《Desalination》2009,249(1):364-367
ZrO2/cordierite composite microfiltration (MF) membrane was prepared by the combination of extrusion and slip casting techniques. The electrokinetic properties of as-prepared membrane were characterized by streaming potential measurements operated in tangential microfiltration mode. The influences of pH, electrolyte species and concentrations of filtered solutions on the electrokinetic properties and permeate flux were investigated. Results show that the streaming potentials are dependent on the pH, types of the electrolyte and concentrations of filtered solutions. The isoelectric point (IEP) of membranes moved from 4.2 to 5.4 with different types of 10− 3 M electrolyte solutions. The change of ionic concentration of NaCl solution does not alter the IEP of the membranes, but does make the streaming potential tend to be zero at high salt concentration. The specific adsorption of Ca2+ and SO42− ions in CaCl2 and Na2SO4 solutions onto the pore wall can alter the IEP and the net charge sign of the membrane. The as-prepared ZrO2/cordierite membrane shows a maximal permeate volume flux near the IEP. 相似文献