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1.
S. K. Poznyak V. V. Kharton J. R. Frade A. A. Yaremchenko E. V. Tsipis S. O. Yakovlev I. P. Marozau 《Journal of Solid State Electrochemistry》2008,12(1):15-30
The behavior of dense ceramic anodes made of perovskite-type (x = 0.30–0.70; y = 0–0.05; z = 0–0.20) and K2NiF4-type (Me = Co, Cu; x = 0–0.20) indicates significant influence of metal hydroxide formation at the electrode surface on the oxygen evolution reaction
(OER) kinetics in alkaline solutions. The overpotential of cobaltite electrodes was found to decrease with time, while cyclic
voltammetry shows the appearance of redox peaks characteristic of Co(OH)2/CoOOH. This is accompanied with increasing effective capacitance estimated from the impedance spectroscopy data, because
of roughening of the ceramic surface. The steady-state polarization curves of in the OER range, including the Tafel slope, are very similar to those of model Co(OH)2–La(OH)3 composite films where the introduction of lanthanum hydroxide leads to decreasing electrochemical activity. La2NiO4-based anodes exhibit a low electrochemical performance and poor stability. The effects of oxygen nonstoichiometry of the
perovskite-related phases are rather negligible at high overpotentials but become significant when the polarization decreases,
a result of increasing role of oxygen intercalation processes. The maximum electrocatalytic activity to OER was observed for
A-site-deficient , where the lanthanum content is relatively low and the Co4+ concentration determined by thermogravimetric analysis is highest compared to other cobaltites. Applying microporous layers
made of template-synthesized nanocrystalline leads to an improved anode performance, although the effects of microstructure and thickness are modest, suggesting a narrow
electrochemical reaction zone. Further enhancement of the OER kinetics can be achieved by electrodeposition of cobalt hydroxide-
and nickel hydroxide-based films.
Dedicated to Professor Dr. Yakov I. Tur’yan on the occasion of his 85th birthday. 相似文献
2.
Li-Hua Bi Sib Sankar Mal Nadeen H. Nsouli Michael H. Dickman Ulrich Kortz Saritha Nellutla Naresh S. Dalal Manuel Prinz Georg Hofmann Manfred Neumann 《Journal of Cluster Science》2008,19(1):259-273
The mixed-valence 24-vanadophosphate
(1) has been synthesized and characterized in the solid state by IR, magnetism, EPR, XPS, and elemental analysis. Single-crystal
X-ray analysis was carried out on (Na-1), which crystallizes in the triclinic system, space group , with a = 17.168(3) ?, b = 18.1971(14) ?, c = 20.1422(13) ?, α = 114.753(3)°, β = 99.390(4)°, γ = 95.124(4)°, and Z = 2. Polyanion 1 has an unusual, open structure composed of 2 RuIIIO6 octahedra, 2 VIVO6 octahedra, 14 VVO5 square-pyramids, 8 VVO4 tetrahedra, and 2 PO4 tetrahedra which are all directly linked via edges and corners. The outer surface of 1 is decorated with six RuII(dmso)3 groups. XPS studies on Na-1 confirm the presence of 2 RuIII and 6 RuII as well as 22 VV and 2 VIV centers. Magnetic susceptibility data on Na-1 show that the VIV–RuIII pairs are coupled antiferromagnetically, with J
1 = −13 K and J
2 ∼ −3 K. We did not detect any peak in our EPR measurements on Na-1, thus supporting the conclusion that Na-1 is diamagnetic in its ground state.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
In Memoriam Prof. F. A. Cotton 相似文献
3.
Jaap F. Vente Steven McIntosh Wim G. Haije Henny J. M. Bouwmeester 《Journal of Solid State Electrochemistry》2006,10(8):581-588
The present paper discusses the oxygen transport properties, oxygen stoichiometry, phase stability, and chemical and mechanical
stability of the perovskites (BSCF) and (SCF) for air separation applications. The low oxygen conductive brownmillerite phase in SCF is characterized using in-situ
neutron diffraction, thermographic analysis and temperature programmed desorption but this phase is not present for BSCF under
the conditions studied. Although both materials show oxygen fluxes well above 10 ml/cm2·min at T=1,273 K and pO2=1 bar for self-supporting, 200 μm-thick membranes, BSCF is preferred as a membrane material due to its phase stability. However,
BSCF’s long-term stable performance remains to be confirmed. The deviation from ideal oxygen stoichiometry for both materials
is high: δ>0.6. The thermal expansion coefficients of BSCF and SCF are 24×10−6 and 30×10−6 K−1, respectively, as determined from neutron diffraction data. The phenomenon of kinetic demixing has been observed at pO2<10−5 bar, resulting in roughening of the surface and enrichment with alkaline earth metals. Stress–strain curves were determined
and indicated creep behavior that induces undesired ductility at T=1,073 K for SCF. Remedies for mechanical and chemical instabilities are discussed. 相似文献
4.
Bo Wang Min-chuan Zhan De-chun Zhu Wei Liu Chu-sheng Chen 《Journal of Solid State Electrochemistry》2006,10(8):625-628
A tubular membrane made of Zr0.8Y0.2O1.9 (60 vol%) and was prepared by a standard ceramic process. Oxygen permeation through the membrane tube was examined by exposing its outer
shell to air and sweeping its inner wall with pure helium or CO balanced with helium. An oxygen flux of 9.2×10−9 mol cm−2 s−1 was measured at 950°C under air/He gradient, and a larger flux of 3.2×10−8 mol cm−2 s−1 at 930°C under air/CO gradient. The membrane tube was found to exhibit excellent stability under highly reducing atmosphere
and elevated temperatures. The oxygen permeation rate is likely to be increased through the modification of the surface and
reduction of the membrane thickness. 相似文献
5.
Oxidation of 3-(4-methoxyphenoxy)-1,2-propanediol (MPPD) by bis(hydrogenperiodato) argentate(III) complex anion, [Ag(HIO6)2]5− has been studied in aqueous alkaline medium by use of conventional spectrophotometry. The major oxidation product of MPPD
has been identified as 3-(4-methoxyphenoxy)-2-ketone-1-propanol by mass spectrometry. The reaction shows overall second-order
kinetics, being first-order in both [Ag(III)] and [MPPD]. The effects of [OH−] and periodate concentration on the observed second-order rate constants k′ have been analyzed, and accordingly an empirical expression has been deduced:
where [IO4
−]tot denotes the total concentration of periodate and k
a = (0.19 ± 0.04) M−1 s−1, k
b = (10.5 ± 0.3) M−2 s−1, and K
1 = (5.0 ± 0.8) × 10−4 M at 25.0 °C and ionic strength of 0.30 M. Activation parameters associated with k
a and k
b have been calculated. A mechanism is proposed, involving two pre-equilibria, leading to formation of a periodato–Ag(III)–MPPD
complex. In the subsequent rate-determining steps, this complex undergoes inner-sphere electron-transfer from the coordinated
MPPD molecule to the metal center by two paths: one path is independent of OH−, while the other is facilitated by a hydroxide ion. 相似文献
6.
Reena Singh Atanu Banerjee Yee Gordon Kajal Krishna Rajak 《Transition Metal Chemistry》2009,34(6):689-694
Abstract The title complexes and have been synthesized in excellent yields by reacting Co(OAc)2·4H2O with H2L1 and H2L2, respectively, in acetonitrile solution. Here, [L1]2− and [L2]2− are the deprotonated forms of N,N-bis(2-hydroxybenzyl)-N′,N′-dimethylethylenediamine and N,N-bis(2-hydroxybenzyl)-2-picolylamine, respectively. The crystal structures of and were determined by x-ray crystallography. In , each cobalt atom has distorted trigonal bipyramid geometry, while in , each cobalt atom has distorted octahedral geometry. Variable temperature magnetic moment measurements show weak antiferromagnetic
interaction in . The magnetic characterization for is in agreement with the presence of Co(II) and Co(III) centers.
Graphical Abstract The title complexes and have been synthesized in excellent yields by reacting Co(OAc)2·4H2O with dianionic N2O2 coordinating ligands. In complex 1, each cobalt atom has distorted trigonal bipyramid geometry, while in complex 2, each
cobalt atom has distorted octahedral geometry. Variable temperature magnetic moment measurements show weak antiferromagnetic
interaction in complex 1. The magnetic characterization for complex 2 is in agreement with the presence of Co(II) and Co(III)
centers.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
7.
The quantitative study of the equilibrium Pu4++Cl−⇋Pu3++1/2 Cl2 in LiCl−KCl (70–30% mol) at 455, 500, 550 and 600°C by visible and near I.R. absorption spectrophotometry allows the calculation
of the reaction's equilibrium constant, the mean thermodynamic data ΔH=27±14 kJ·mol−1 and ΔS=37±17 J·mol−1·K−1 and the standard potential of the couple
.
相似文献
8.
The kinetics of hexacyanoferrate(III) reduction by hydrogen peroxide in strongly alkaline media leading to hexacyanoferrate(II)
ion have been studied spectrophotometrically within the wavelength range 300–500 nm. The reaction obeys a simple pseudo-first-order
rate expression under the applied conditions, namely, a large excess of the reductant and OH− anion concentrations, and a low oxidant concentration. The linear dependences of the pseudo-first-order rate constant on
OH− and H2O2 concentrations are consistent with the rate law of the form: where and are the second- and the pseudo-third-order rate constants for the electron transfer from HO2
− and O2
2− to [Fe(CN)6]3−, respectively. The apparent activation parameters determined at 0.4 M NaOH are as follows: ΔH
# = (18.0 ± 1.0) kJ mol−1 and ΔS
# = (−155 ± 3.5) J K−1 mol−1. The possible mechanism of the reaction is discussed. 相似文献
9.
Reinaldo F. Teófilo Helder J. Ceragioli Alfredo C. Peterlevitz Leonardo M. Da Silva Flavio S. Damos Márcia M. C. Ferreira Vitor Baranauskas Lauro T. Kubota 《Journal of Solid State Electrochemistry》2007,11(10):1449-1457
The electrochemical properties of boron-doped diamond (BDD) polycrystalline films grown on tungsten wire substrates using
ethanol as a precursor are described. The results obtained show that the use of ethanol improves the electrochemistry properties
of “as-grown” BDD, as it minimizes the graphitic phase upon the surface of BDD, during the growth process. The BDD electrodes
were characterized by Raman spectroscopy, scanning electronic microscopy, cyclic voltammetry (CV), and electrochemical impedance
spectroscopy (EIS). The boron-doping levels of the films were estimated to be ∼1020 B/cm3. The electrochemical behavior was evaluated using the and redox couples and dopamine. Apparent heterogeneous electro-transfer rate constants were determined for these redox systems using the CV and EIS techniques. values in the range of 0.01–0.1 cm s−1 were observed for the and redox couples, while in the special case of dopamine, a lower value of 10−5 cm s−1 was found. The obtained results showed that the use of CH3CH2OH (ethanol) as a carbon source constitutes a promising alternative for manufacturing BDD electrodes for electroanalytical
applications. 相似文献
10.
The electropolymerization of aniline on a palladized aluminum electrode (Pd/Al) by potentiodynamic as well as potentiostatic
methods is described. The effect of the monomer concentration between 0.01 and 0.4 M on the polyaniline (PANI) formation and
its growth on the Pd/Al electrode was investigated and a suitable concentration of 0.2 M is suggested. A similar study was
carried out to investigate the effect of sulfuric acid concentration and 0.1 M sulfuric acid was chosen. A study on the influence
of electropalladization time on the polymer formation and its growth suggested a convenient time of 40 s. The stability of
the PANI film on the Pd/Al electrode was studied as function of the potential imposed on the electrode. For applied electrode
potentials of 0.1–0.7 V, the first-order degradation rate constant, k, of PANI film varies between 1×10−6 and 2×10−5 s−1, and a relatively low slope (i.e., 2.2) was obtained for the plot of log k versus E. The coatings were characterized by scanning electron microscopy (SEM), and cyclic voltammetric behavior of the PANI-deposited
Pd/Al electrode is discussed. The electrocatalytic activity of the PANI-deposited Pd/Al electrode against para-benzoquinone/hydroquinone (Q/H2Q) and redox systems were investigated and on the basis of of the corresponding cyclic voltammograms and the redox systems were identified as the reversible and quasi-reversible systems,
respectively. 相似文献
11.
This work reports on the removal of organic matter and nitrogen in a radial-flow aerobic-anoxic immobilized biomass (RAIB)
reactor fed with domestic sewage pretreated in a horizontal-flow anaerobic immobilized biomass (HAIB) reactor. Polyurethane
foam was used as support material for biomass attachment in both reactors. In batch experiments, a first-order kinetic model
with residual concentration represented the organic matter removal rate, whereas nitrogen conversion followed a pseudo-first-order
reaction in series model, with kinetic constants k
1 (ammonium to nitrite) and k
2 (nitrite to nitrate) of 0.25 and 6.62 h−1, respectively. The RAIB reactor was operated in continuous-flow mode and changes in the airflow rate and hydraulic retention
time were found to interfere in the apparent kinetic constants to the nitritation (k
1) and nitratation (k
2). Nitrification and denitrification were achieved in the partially aerated RAIB reactor operating with hydraulic retention
times of 3.3 h and 2.7 h in the aerobic and anoxic zones, respectively. Ethanol was added in the anoxic zone of the reactor
to promote denitrification. The effluent flow of the RAIB reactor presented a COD of 52 mg l−1, and concentrations of 2 mg , 1.24 mg and 3.46 mg . 相似文献
12.
Hilde Lea Lein Øystein Skottun Andersen Per Erik Vullum Edgar Lara-Curzio Randi Holmestad Mari-Ann Einarsrud Tor Grande 《Journal of Solid State Electrochemistry》2006,10(8):635-642
Young’s modulus, strain–stress behavior, fracture strength, and fracture toughness of (0≤×≤1) materials have been investigated in the temperature range 20–1,000°C. Young’s moduli of and , measured by resonant ultrasound spectroscopy, were 130±1 and 133±3 GPa, respectively. The nonlinear stress–strain relationship
observed by four-point bending at room temperature was inferred as a signature of ferroelastic behavior of the materials.
Above the ferroelastic to paraelastic transition temperature, the materials showed elastic behavior, but due to high-temperature
creep, a nonelastic respond reappeared above ∼800°C. The room temperature fracture strength measured by four-point bending
was in the range 107–128 MPa. The corresponding fracture toughness of , measured by single edge V-notch beam method, was 1.16±0.12 MPa·m1/2. The measured fracture strength and fracture toughness were observed to increase with increasing temperature. The fracture
mode changed from intragranular at low temperature to intergranular at high temperature. Tensile stress gradient at the surface
of the materials caused by a frozen-in gradient in the oxygen content during cooling was proposed to explain the low ambient
temperature fracture strength and toughness. 相似文献
13.
Yanluo Lu Lan Yang Min Wei Yaning Xie Tao Liu 《Journal of Solid State Electrochemistry》2007,11(9):1157-1162
Supramolecular pillared oxides were prepared through the intercalation of M2+ cations into a MnO2 host matrix by the method of ion exchange between the precursor δ-K
x
MnO2 and the corresponding guest. The materials M-MnO2 crystallize in the hexagonal system, the same structure as the precursor, with a larger interlamellar spacing. In the case
of ZrO-MnO2, extended X-ray absorption fine structure (EXAFS) determination indicates that the Zr atom locates between the MnO2 layers forming a stable structure. Compared with the precursor, the cycling property of M-MnO2 was improved distinctly, while the capacity decreased to some degree due to the strong interaction between pillars and the
host matrix. Among these pillared materials, ZrO-MnO2 has an advanced reversible capacity of 161.5 mAh·g−1 and improved cycling behavior compared with the precursor. 相似文献
14.
Defne Bayraktar Stefan Diethelm Peter Holtappels Thomas Graule Jan Van herle 《Journal of Solid State Electrochemistry》2006,10(8):589-596
The influence of partial substitution of Fe with Ti on the oxygen transport properties of La1−x
Sr
x
FeO3 membranes was investigated in view of their application for oxygen separation. Samples of composition (y=0, 0.2) were prepared and their oxygen transport properties characterised by potential step relaxation and by oxygen permeation
measurement in an air/argon gradient. With the first technique, chemical diffusion and surface exchange (k
S) coefficients were obtained by fitting of the current relaxation data to a single expression valid over the complete time
range. The Ti-substituted composition gave slightly larger values of and k
S. The trend was opposite for the measured oxygen permeation flux. In the latter experience, ordering of oxygen vacancies was
observed at lower temperature, reducing significantly the performance of the material. 相似文献
15.
The oxidation of H2NOH is first-order both in [NH3OH+] and [AuCl4
–]. The rate is increased by the increase in [Cl–] and decreased with increase in [H+]. The stoichiometry ratio, [NH3OH+]/[AuCl4
–], is 1. The mechanism consists of the following reactions.
The rate law deduced from the reactions (i)–(iv) is given by Equation (v) considering that [H+] K
a.
The reaction (iii) is a combination of the following reactions:
The activation parameters for the reactions (ii) and (iii) are consistent with an outer-sphere electron transfer mechanism. 相似文献
16.
Solubility of Oxygen in Some 1-1, 2-1, 1-2, and 2-2 Electrolytes as a Function of Concentration at 25°C 总被引:1,自引:0,他引:1
The solubility of oxygen has been measured in a number of electrolytes [(LiCl, KCl, RbCl, CsCl, NaF, NaBr, NaI, NaNO3, KBr, KI, KNO3, CaCl2, SrCl2, BaCl2, Li2SO4, K2SO4, Mn(NO3)3)] as a function of concentration at 25°C. The solubilities, mol (kg-H2O)–1, have been fitted to a function of the molality m (standard deviation < 3mol-kg–1)
where A and B are adjustable parameters and the activity coefficient of oxygen )O2) = [O2]0/[O2]. The limiting salting coefficient, k
S = (ln / m)m=0 = A, was determined for all salts. The salting coefficients for the chlorides and sodium salts showed a near linear correlation with the crystal molar volume V
cryst = 2.52 r
3. The salting coefficients determined from the Scaled Particle Theory were in reasonable agreement with the measured values. The activity coefficients of oxygen in the solutions have been interpreted using the Pitzer equation
where
is a parameter that accounts for the interaction of O2 with cations (c) and anions (a) with molalities m
a and m
c, and
accounts for interactions for O2 with the cation and anion pair (c-a). The
and
coefficients determined for the most of the ions are in reasonable agreement with the tabulations of Clegg and Brimblecombe. The values of
for most of the ions are a linear function of the electrostriction molar volume (Velect = V0 – V
cryst). 相似文献
17.
K. S. Gupta R. K. Mehta A. K. Sharma P. K. Mudgal S. P. Bansal 《Transition Metal Chemistry》2008,33(7):809-817
For getting an insight into the mechanism of atmospheric autoxidation of sulfur(IV), the kinetics of this autoxidation reaction
catalyzed by CoO, Co2O3 and Ni2O3 in buffered alkaline medium has been studied, and found to be defined by Eqs. I and II for catalysis by cobalt oxides and
Ni2O3, respectively.
The values of empirical rate parameters were: A{0.22(CoO), 0.8 L mol−1s−1 (Co2O3)}, K
1{2.5 × 102 (Ni2O3)}, K
2{2.5 × 102(CoO), 0.6 × 102 (Co2O3)} and k
1{5.0 × 10−2(Ni2O3), 1.0 × 10−6(CoO), 1.7 × 10−5 s−1(Co2O3)} at pH 8.20 (CoO and Co2O3) and pH 7.05 (Ni2O3) and 30 °C. This is perhaps the first study in which the detailed kinetics in the presence of ethanol, a well known free
radical scavenger for oxysulfur radicals, has been carried out, and the rate laws for catalysis by cobalt oxides and Ni2O3 in the presence of ethanol were Eqs. III and IV, respectively.
For comparison, the effect of ethanol on these catalytic reactions was studied in acidic medium also. In addition, alkaline
medium, the values of the inhibition factor C were 1.9 × 104 and 4.0 × 103 L mol−1 s for CoO and Co2O3, respectively; for Ni2O3, C was only 3.0 × 102 only. On the other hand, in acidic medium, the values of this factor were all low: 20 (CoO), 0.7 (Co2O3) and 1.4 (Ni2O3). Based on these results, a radical mechanism for CoO and Co2O3 catalysis in alkaline medium, and a nonradical mechanism for Ni2O3 in both alkaline and acidic media and for cobalt oxides in acidic media are proposed. 相似文献
(I) |
(II) |
(III) |
(IV) |
18.
The mechanism of the Co(II) catalytic electroreduction of water insoluble CoR2 salt in the presence of cysteine was developed. CoR2 = cobalt(II) cyclohexylbutyrate is the component of a carbon paste electrode. Electrode surface consecutive reactions are:
(a) fast (equilibrium) reaction of the complex formation, (b) rate-determining reversible reaction of the promoting process of CoR(Ac+) complex formation, (c) rate-determining irreversible reaction of the electroactive complex formation with ligand-induced adsorption, and (d) fast irreversible reaction of the electroreduction. Reactions (a,b) connected with CoR2 dissolution and reactions (c,d) connected with CoR2 electroreduction are catalyzed by . Regeneration of (reactions “b,d”) and accumulation of atomic Co(0) (reaction “d”) take place. Experimental data [Sugawara et al., Bioelectrochem
Bioenergetics 26:469, 1991]: i
a vs E (i
a is anodic peak, E is cathodic accumulation potential), i
a vs , and i
a vs pH have been quantitatively explained. 相似文献
19.
The coupling reaction of 4-aminoantipyrine (4-AAP) with phenol using the superoxide anion radical (
) as oxidizing agent under the catalysis of horseradish peroxidase (HRP) was studied. Based on the reaction,
produced by irradiating vitamin B2 (VB2) was spectrophotometrically determined at 510 nm. Under the optimum experimental conditions, the relationship between A
510 and
concentration was linear in the range 9.14×10–6–1.2×10–4 mol L–1. The detection limit was determined to be 1.37×10–6 mol L–1. A possible reaction mechanism was discussed. The effect of interferences and surfactants on the determination of
was also investigated. The proposed method was applied to determine superoxide dismutase activity in garlic, scallion, and onion with satisfactory results. 相似文献
20.
K. Juodkazis J. Juodkazytė R. Vilkauskaitė V. Jasulaitienė 《Journal of Solid State Electrochemistry》2008,12(11):1469-1479
The processes of nickel surface anodic oxidation taking place within the range of potentials preceding oxygen evolution reaction
(OER) in the solutions of 1 M KOH, 0.5 M K2SO4, and 0.5 M H2SO4 have been analyzed in the present paper. Metallic nickel, thermally oxidized nickel, and black nickel coating were used as
Ni electrodes. The methods of cyclic voltammetry and X-ray photoelectron spectroscopy were employed. The study was undertaken
with a view to find the evidence of peroxide-type nickel surface compounds formation in the course of OER on the Ni electrode
surface. On the basis of experimental results and literature data, it has been suggested that in alkaline solution at E ≈ 1.5 V (RHE) reversible electrochemical formation of Ni(IV) peroxide takes place according to the reaction as follows: This reaction accounts for both the underpotential (with respect to ) formation of O2 from NiOO2 peroxide and also small experimental values of dE/dlgi slope (<60 mV) at low anodic current densities, which are characteristic for the two-electron transfer process. It has been
inferred that the composition of the γ-NiOOH phase, indicated in the Bode and revised Pourbaix diagrams, should be ∼5/6 NiOOH + ∼1/6
NiOO2. The schemes demonstrating potential-dependent transitions between Ni surface oxygen compounds are presented, and the electrocatalytic
mechanisms of OER in alkaline, acid, and neutral medium have been proposed. 相似文献