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1.
Y. M. Volfkovich D. A. Bograchev A. A. Mikhalin V. S. Bagotsky 《Journal of Solid State Electrochemistry》2014,18(5):1351-1363
Electrochemical behavior of electrodes on the basis of CH900-20 activated carbon (AC) cloth has been studied in concentrated sulfuric acid solution. Cyclic voltammetric curves have been studied in the reversibility range (from 0.1 to 0.9 V RHE) and in the deep cathodic charging potential range (from –0.8 to 1 V RHE). It has been shown that electric double layer (EDL) charging occurs in the reversibility range, while faradaic processes of hydrogen intercalation into AC carbon take place in the range of negative potentials (←0.1 V). The intercalation process is governed by slow solid-phase hydrogen diffusion. The specific charge value grows at an increase in concentrated sulfuric acid solution. The mechanism of double intercalation of sulfuric acid and hydrogen into the AC material is suggested. On the basis of the reached specific discharge capacitance of 1,560 C/g (or 1,110 F/g) and Faraday's law, it has been concluded that the compound of C6H is formed in the limiting case of deepest cathodic charging. The obtained data have been used in a mathematical charge–discharge model for an AC electrode taking into account the EDL charging and the hydrogen intercalation. The galvanostatic recharge curves have been calculated in the diapason of currents by the developed model. 相似文献
2.
The electroreduction of metol on mechanically renewed metallic electrodes is studied by direct voltammetry with linear potential
sweep. Reduction peaks of metol are found in a neutral supporting electrolyte (0.02–0.5 M Na2SO4) on nickel, silver, and mercury electrodes before the potential of hydrogen liberation from the supporting electrolyte. The
shape and parameters of the cathodic peak depend on an electrode material, and also on the composition and pH of the supporting
solution. A probable mechanism of the electroreduction of metol is proposed. The regeneration of nickel and silver electrodes
by in situ mechanical cutting of a 0.5-μm surface layer provides good reproducibility of the value of peak current; it is
proportional to the concentration of metol in the range 2 × 10−3–1.8 × 10−2 M. 相似文献
3.
A cathodic differential pulse voltammetric determination of colchicine was validated using a glassy carbon electrode in HClO4/H3PO4 0.01 M. Colchicine gives an irreversible, diffusion-controlled peak at −862 mV vs. Ag/AgCl reference electrode. The cathodic
peak is strongly influenced by a more alkaline environment with a shift towards more negative potentials. Method optimization
was carried out in parallel for three types of electrodes (glassy carbon, mercury film and bismuth film coated glassy carbon).
The cathodic peak current is higher using film-coated electrodes, but shows poorer intra-day reproducibility and a longer
analysis time due to film renewal. Thus, a bare glassy carbon electrode was used to determine colchicine in the concentration
range of 2.4 − 50 μg mL−1 (R
2 = 0.9998, n = 5), with a calculated detection limit of 0.80 μg mL−1. The proposed method was characterized according to ICH Harmonized Tripartite Guidance Q2(R1) by validation parameters (selectivity,
linearity, accuracy, fidelity, limit of detection, limit of quantification) and it was successfully applied for the determination
of colchicine from tablets, without the interference of the excipients. The method’s performances were evaluated and compared
with both a known polarographic method and the official quantitative spectrophotometric determination from the Romanian Pharmacopoeia,
Xth edition, respectively.
相似文献
4.
Pt/SO4
2−−ZrO2 calcined at 873 K shows the same catalytic activity forn-hexane isomerization as the calcined and reduced sample. A platinum reduction peak did not appear in the TPR profile and
the presence of Pt0 was detected by XPS on the only calcined Pt/SO4
2−−ZrO2. Nevertheless, this calcined material does not show hydrogen chemisorption and cyclohexane dehydrogenation activity. 相似文献
5.
Jelena S. ?or?evi? Ana M. Kalijadis Ksenija R. Kumri? Zoran M. Jovanovi? Zoran V. Lau?evi? Tatjana M. Trti?-Petrovi? 《Central European Journal of Chemistry》2012,10(4):1271-1279
In this study the application of home-made unmodified (GC) and bulk modified boron doped glassy carbon (GCB) electrodes for the voltammetric determination of the linuron was investigated. The electrodes were synthesized with a moderate temperature treatment (1000°C). Obtained results were compared with the electrochemical determination of the linuron using a commercial glassy carbon electrode (GC-Metrohm). The peak potential (E p ) of linuron oxidation in 0.1 mol dm−3 H2SO4 as electrolyte was similar for all applied electrodes: 1.31, 1.34 and 1.28 V for GCB, GC and GC-Metrohm electrodes, respectively. Potential of linuron oxidation and current density depend on the pH of supporting electrolyte. Applying GCB and GC-Metrohm electrodes the most intensive electrochemical response for linuron was obtained in strongly acidic solution (0.1 mol dm−3 H2SO4). Applying the boron doped glassy carbon electrode the broadest linear range (0.005–0.1 μmol cm−3) for the linuron determination was obtained. The results of voltammetric determination of the linuron in spiked water samples showed good correlation between added and found amounts of linuron and also are in good agreement with the results obtained by HPLC-UV method. This appears to be the first application of a boron doped glassy carbon electrode for voltammetric determination of the environmental important compounds. 相似文献
6.
7.
Ivo Paseka 《Journal of Solid State Electrochemistry》2007,11(1):52-58
Electrochemical voltammetric curves on Ru and Pt blacks of a different surface area were measured in potential intervals 0.05–1.05 V
in pure 0.5 M H2SO4 and after CO adsorption. It was proved that after the CO adsorption, the outset of ruthenium oxidation is shifted by about
150 mV towards the positive potentials, e.g. to the region of oxidation of adsorbed CO. This fact made possible the determination
of a double-layer charging current of Ru electrodes and, subsequently, also the determination of the amount of adsorbed hydrogen
on the Ru surface. An evaluation of the amount of CO and hydrogen adsorption showed that the ratio of adsorbed CO:H on the
Pt surface was about 1:1, while on Ru electrodes this ratio was around twice as large. The amount of hydrogen adsorbed on
Ru blacks depends on the preliminary preparation of the electrodes. The CO adsorption could also be employed in the determination
of a charging current of electrode double-layers during voltammetric oxidation of adsorbed hydrogen on ruthenium supported
on Al2O3, SiO2, or TiO2 carriers. However, a similar determination of hydrogen adsorbed on the tin-modified Ru catalysts is not very reliable. 相似文献
8.
The adsorption of iodine and iodide anions on a Pt/Pt electrode (0.5 M H2SO4 as a supporting solution) is compared using potentiodynamic and galvanostatic charging curves, transients of the current and open-circuit potential (OCP), and analytical measurements. Variations in the charge and OCP during the adsorption obey relationships derived for strong adsorption of neutral species and ions on a hydrogen electrode with the formation of irreversibly adsorbed atoms. The main product of the I2 and I– chemisorption in acid solutions is adsorbed iodine atoms. However, adsorption of iodine occurs in noticeable amounts and above a monolayer in the form of species that undergo electrodesorption during a cathodic polarization to potentials of the beginning of hydrogen adsorption. In the presence of a monolayer of adsorbed iodine atoms, potential of the zero total charge of a Pt/Pt electrode is in the oxygen adsorption region. 相似文献
9.
A. Survila Z. Mockus S. Kanapeckaite J. Pileckiene G. Stalnionis 《Russian Journal of Electrochemistry》2011,47(2):129-135
The kinetics of cathodic processes proceeding in the acidic 0.01 M Cu(II) solutions containing gluconic acid and 0.5 M Na2SO4 as the supporting electrolyte is studied. According to the spectrophotometric data, in the moderately acidic solutions, a
monoligand complex of CuL+ predominantly forms. Its concentration stability constant is 102.2 M−1. In the cathodic voltammograms, a well-defined plateau of the limiting current is observed. The height of the plateau obeys
the Levich equation. The effective diffusion coefficient decreases from 4.2 × 10−6 to 2.5 × 10−6 cm2/s with increasing complexation degree of the system. An analysis of normalized Tafel plots showed that the exchange current
density of Cu2+ + e → Cu+ process decreases with increasing concentration of ligand or with increasing pH value. Thereby, the cathodic chargetransfer
coefficient remains constant (0.33 ± 0.02). A comparison of the kinetic data with the results of deposit surface examination
points to significant surface activity of the ligand. The gluconate chemisorption can be accompanied by the incorporation
of the fragments, which were formed as a result of its destruction, into the electrodeposits. 相似文献
10.
Iron oxide development is necessary as the Iron electrodes exhibit high self discharge and poor charging efficiency in alkaline
batteries. Pressed electrodes containing electrolytic iron powder with varying amounts of Fe3O4 have been used. The variation of open circuit potential and self discharge currents with alkali concentration is followed.
For better understanding of these variations, cyclic polarisation (−1.3 V to + 0.4 Vvs Hg/HgO) and hydrogen evolution studies are carried out. Beyond −0.5 Vvs Hg/HgO, the surface is covered by hydrolysed layer and the protons diffuse away from this layer. The hydrogen evolution takes
place with the discharge of K+ ions as the rate determining step. 相似文献
11.
The overpotential of nickel ion electroreduction on the nickel and mercury electrodes is shown to increase in the following
sequence of anions: ClO4−,CH3SO3−, SO42−. On the nickel electrode, the overpotential of nickel evolution decreases as the pHv increases from 1.5 to 4. This is associated with the increase in pHs as the result of a parallel reaction of hydrogen evolution. It is shown that in contrast to mercury, the Tafel plots of the
nickel electrode demonstrate a bend corresponding to the change in their slope from −0.044 to −0.132 V. This is accompanied
by the lowering down of the reaction order in nickel ions from 2 to 1. A mechanism of nickel ion electroreduction that includes
two parallel routes is proposed and substantiated by a model. In the low overpotential range, the predominant process is the
electroreduction of nickel hydroxocomplexes, which is characterized by the strong dependence of the reaction rate on the potential
and the concentration of electroactive species. For high overpotentials, the predominant process is the direct discharge of
nickel aquacomplexes the rate of which depends weaker on the potential and the concentration of electroactive species. 相似文献
12.
M. A. Zanjanch Sh. Sohrabnezhad M. Arvand M. F. Mousavi 《Russian Journal of Electrochemistry》2007,43(7):758-763
The electrochemical properties of thionine dye adsorbed into ZSM-5 and HZSM-5 zeolites (TH/ZSM-5, TH/HZSM-5) are studied in
0.5 M KCl solution. The dye is strongly retained and not easily leached from the zeolites matrix. The samples are incorporated
into the carbon paste electrode (TH/ZSM-5/P, TH/HZSM-5/P) for cyclic voltammetric measurements. The redox reactions of thionine
incorporated into ZSM-5 zeolite contain a quasi-reversible, two-electron one proton in the pH range 1 to 10, but thionine-loaded
HZSM-5 zeolite undergoes a quasi-reversible two-electron two-protons redox reaction under acidic conditions and a one proton
two-electron redox reaction takes place under basic conditions. The separation of the anodic and cathodic potentials (E
p) is high in thionine-loaded zeolites (>100) with respect to the solution of thionine (E
p = 34 for ZSM-5/P and 36 mV for HZSM-5/P), indicating that there are strong interaction between thionine molecules and the
zeolites. The midpoint potentials (E
m) for TH/ZSM-5/P and TH/HZSM-5/P are −0.203 and −0.381 V, respectively. However, the midpoint potentials for the solution
of thionine for the electrode system of ZSM-5/P and HZSM-5/P are −0.335 and −0.407 V, respectively. Thus, thionine dye molecules
incorporated into the zeolites can be reduced more easily with respect to solution of thionine. In various electrolyte solutions,
the midpoint potentials remains constant, but the midpoint potential of the thionine-zeolite electrodes depends on the solution
pH. Influence of the pH of the solution on the midpoint potential of an immobilized dye reveals that thionine molecules are
accessible to protons. This property is ascribed to the formation of mesopores in the structure of our zeolites suffering
from a calcination step.
Published in Russian in Elektrokhimiya, 2007, Vol. 43, No. 7, pp. 794–800.
The text was submitted by the authors in English 相似文献
13.
SiO2/Sb2O3 (SiSb), having a specific surface area, S
BET, of 788 m2 g−1, an average pore diameter of 1.9 nm and 4.7 wt% of Sb, was prepared by the sol-gel processing method. Meldola's blue (MeB),
methylene blue (MB) and toluidine blue (TB) were immobilized on SiSb by an ion exchange reaction. The amounts of the dyes
bonded to the substrate surface were 12.49, 14.26 and 22.78 μmol g−1 for MeB, MB and TB, respectively. These materials were used to modify carbon paste electrodes. The midpoint potentials (E
m) of the immobilized dyes were −0.059, −0.17 and −0.18 V vs. SCE for SiSb/MeB, SiSb/MB and SiSb/TB modified carbon paste electrodes,
respectively. A solution pH between 3 and 7 practically did not affect the midpoint potential of the immobilized dyes. The
electrodes presented reproducible responses and were chemically stable under various oxidation-reduction cycles. Among the
immobilized dyes, MeB was the most efficient to mediate the electron transfer for NADH oxidation in aqueous solution at pH 7.
In this case, amperometric detection of NADH at an applied potential of 0 mV vs. SCE gives linear responses over the concentration
range of 0.1–0.6 mmol L−1, with a detection limit of 7 μmol L−1. 相似文献
14.
M. Jayakumar K. A. Venkatesan T. G. Srinivasan P. R. Vasudeva Rao 《Journal of Radioanalytical and Nuclear Chemistry》2010,284(1):79-85
The electrochemical behavior of ruthenium(III) and rhodium(III) in nitric acid medium has been studied at platinum and stainless
steel electrodes by cyclic voltammetry. The cyclic voltammograms consisted of surge in cathodic current occurring at potentials
of −0.13 V (Vs. Pd) and −0.15 V (Vs. Pd), which culminates into peaks at −0.47 V and −0.5 V due to the reductions of Ru(III)
and Rh(III) to their metallic forms, respectively. Electrodeposition was carried out at stainless steel electrode and unlike
palladium, the recovery of ruthenium and rhodium was limited to ~4% and ~14%, respectively. However, a different scenario
was observed in case of electrodeposition from a ternary solution containing all these platinum metals. Ruthenium and rhodium
deposited underpotentially in the presence of palladium and the recovery of ~20% and ~5% was observed for ruthenium and rhodium,
respectively. Evolution of RuO4 at the anode and deposition of RuO2 in the anodic side was observed in all cases during electrolysis of ruthenium(III) containing solutions. 相似文献
15.
Ljubomir D. Arsov 《Journal of Solid State Electrochemistry》1998,2(4):266-272
The electrochemical synthesis of polyaniline on a titanium surface in aqueous sulfuric acid solutions with various concentrations
of added aniline has been investigated by cyclic voltammetry. By utilizing a more cathodic potential range (up to −0.6 V)
for the cyclization than is usual (up to −0.2 V) on Pt and Au electrodes, the new voltammetric waves have been deconvoluted
from the already well-known ones for polyaniline.
By simultaneous electrochemical and in situ Raman spectroscopic measurements, the Raman bands of polyaniline electrodeposited
on a Ti electrode, were assigned for potentials of −0.15 V and −0.6 V. It was found that the new monitored waves were closely
related to the so-called “middle” peaks and appear only when the polyaniline reaches an overoxidized state.
Received: 7 August 1997 / Accepted: 4 November 1997 相似文献
16.
Nickel foam and five nickel foam-based composite electrodes were prepared for being used as anode materials for the electrooxidation
of methanol in KOH solution containing 0.1 and 1.0 M of methanol. The layered electrodes composed of nickel foam, platinum
nanoparticles, polyaniline (PANI) and/or porous carbon (C) prepared in various assemblies. As shown by SEM analysis, depending
on the preparation conditions, the electrodes of different morphologies were obtained. Using the cyclic voltammetry method,
the oxidation of methanol on nickel foam electrode was observed in the potential range 0.4 V ↔ 0.7 V, where the Ni(OH)2/NiOOH transformation occurred. The presence of Pt particles in electrode gave rise to the increase in electrocatalytic activity
in this potential range. For electrodes containing dispersed platinum catalyst (Ni/Pt, Ni/PANI/Pt and Ni/C/Pt), the oxidation
of methanol was noted also in the potential range −0.5 V ↔ 0.1 V. The electrocatalytic activities of the examined electrodes
toward methanol oxidation at low potentials were in order Ni/Pt > Ni/C/Pt > Ni/PANI/Pt, whereas at high potentials in order
Ni/PANI/Pt > Ni/Pt> Ni/C/Pt > Ni. Among the examined electrodes, the most resistant to cyclic poisoning appeared to be the
Ni/C/Pt electrode.
Presented at the 4Th Baltic Conference on Electrochemistry, Greifswald, March 13–16, 2005 相似文献
17.
The reduction of SO2 on Pt and glassy carbon electrodes in acetonitrile-0.1 M LiBr solutions is studied by chronopotentiometric and chronovoltamperometric techniques in a wide range of SO2 concentrations. It is found that the reduction process involves an irreversible adsorption of the reaction products followed by a fast formation of a weakly soluble dithionate film which passivates the electrode surface. At sweep rates >0.1 V s?1 the electric charge associated with cathodic reaction corresponds to that of a monolayer. The dependencies of the peak current and the peak potential on the sweep rate are in agreement with the requirements of the adsorption pseudocapacitance theory. The strong effect of water on the height of the cathodic peaks is indicative of the depassivation of the electrode by some active species formed in the presence of water, SO2 and LiBr by a slow reaction. 相似文献
18.
Galyna Shul Maria A. Murphy Geoff D. Wilcox Frank Marken Marcin Opallo 《Journal of Solid State Electrochemistry》2005,9(12):874-881
Composite electrodes were prepared from chemical vapor deposition grown carbon nanofibers consisting predominantly of ca.
100 nm diameter fibers. A hydrophobic sol–gel matrix based on a methyl-trimethoxysilane precursor was employed and composites
formed with carbon nanofiber or carbon nanofiber—carbon particle mixtures (carbon ceramic electrode). Scanning electron microscopy
images and electrochemical measurements show that the composite materials exhibit high surface area with some degree of electrolyte
solution penetration into the electrode. These electrodes were modified with redox probe solution in 2-nitrophenyloctylether.
A second type of composite electrode was prepared by simple pasting of carbon nanofibers and the same solution (carbon paste
electrode). For both types of electrodes it is shown that high surface area carbon nanofibers dominate the electrode process
and enhance voltammetric currents for the transfer of anions at liquid|liquid phase boundaries presumably by extending the
triple-phase boundary. Both anion insertion and cation expulsion processes were observed driven by the electro-oxidation of
decamethylferrocene within the organic phase. A stronger current response is observed for the more hydrophobic anions like
ClO4− or PF6− when compared to that for the more hydrophilic anions like F− and SO42−.
Presented at the 4th Baltic Conference on Electrochemistry, Greifswald, March 13–16, 2005 相似文献
19.
V. V. Kuznetsov B. I. Podlovchenko K. V. Kavyrshina Yu. M. Maksimov 《Russian Journal of Electrochemistry》2010,46(12):1353-1359
The electrocatalytic Pt-Mo system was obtained by formation of platinum particles on the Mo surface under its contact with
PtC62− (PtCl42−) under the open circuit conditions. Cyclic voltammograms of the obtained Pt(Mo) electrodes feature well pronounced peaks
of hydrogen adsorption and desorption on Pt particles. Nonuniform platinum distribution across the electrode surface was found.
Pt(Mo) electrodes showed a higher specific activity in the reaction of methanol oxidation in the potential range of 0.35–0.45
V (RHE) as compared to Pt/Pt. 相似文献
20.
LI Mingyu XIONG Lin CHEN Yunyun ZHANG Na ZHANG Yuanming & YIN Hua .Department of Environmental Engineering Jinan University Guangzhou China .Department of Chemistry Jinan University Guangzhou China 《中国科学B辑(英文版)》2005,48(4):297-304
The photocatalytic oxidation of poisonous or nonbiodegradable organic pollutants in wastewater has been the focus of numerous environmental investiga- tions in recent years. Selecting excellent-performance photocatalytic material is very important in thes… 相似文献