Search results for " ELECTROLYTE"
showing 10 items of 106 documents
Nature of (C5Me5)2Mo2O5in water–methanol at pH 0–14. On the existence of (C5Me5)MoO2(OH) and (C5Me5)MoO2+: a stopped-flow kinetic analysis
2002
A stopped-flow analysis of compound Cp*2Mo2O5 (Cp* = η5-C5Me5) in 20% MeOH–H2O over the pH range 0–14 has provided the speciation of this molecule as well as the rate and mechanism of interconversion between the various species that are present in solution. The compound is a strong electrolyte in this solvent combination, producing the Cp*MoO2+ and Cp*MoO3− ions in equilibrium with a small amount of Cp*MoO2(OH), the latter attaining ca. 15% relative amount at pH 4. At low pH ( 6. The acid dissociation constant of Cp*MoO2(OH) has been measured directly (pK = 3.65 ± 0.02) while the pK for the protonation equilibrium leading to Cp*MoO3H2+ is estimated as 5. The prevalent pathway at high pH i…
Electrochemical and spectroelectrochemical studies of β-phosphorylated Zn porphyrins
2013
The electrochemical and spectroelectrochemical properties of two β-phosphorylated Zn porphyrins, [2-diethoxyphosphoryl-5,10,15,20-tetraphenylporphyrinato]zinc (1) and [2-diisopropoxyphosphoryl-5,10,15,20-tetraphenylporphyrinato]zinc (2), are reported in CH 2 Cl 2 and PhCN containing tetrabutylammonium perchlorate (TBAP) or tetrabutylammonium hexafluorophosphate (TBAPF6) as supporting electrolyte. Under certain solution conditions, three one-electron reductions are observed, with the last process being attributed to the product of a chemical reaction following formation of the porphyrin dianion. Two or three oxidations are observed for the same compounds, again depending upon the solution c…
Prognostic value of N-terminal pro-brain natriuretic peptide in elderly people with acute myocardial infarction: prospective observational study
2009
Objective To examine the influence of age on the predictive value of N-terminal pro-brain natriuretic (NT-proBNP) peptide assay in acute myocardial infarction. Design Prospective observational study. Setting All intensive care units in one French region. Participants 3291 consecutive patients admitted for an acute myocardial infarction, from the RICO survey (a French regional survey for acute myocardial infarction). Main outcome measure Cardiovascular death at 1 year. Results Among the 3291 participants, mean age was 68 (SD 14) years and 2356 (72%) were men. In the study population, the median NT-proBNP concentration was 1053 (interquartile range 300-3472) pg/ml. Median values for age quart…
On the Existence of Different Zeolite-Associated Topological Redox Isomers. Electrochemistry of the Y Zeolite-Associated Mn(Salen)N3 Complex
2002
The electrochemical properties of Y zeolite-associated MnIII(salen)N3 (salen = trans-(R,R)-1,2-bis(salicyldeneamino)cyclohexane) has been investigated using polymer film electrodes immersed into neutral aqueous solutions. Zeolite Y-associated Mn(III)−salen complexes are reduced in one-electron reversible process at −0.25 V versus SCE. The electrochemical response is discussed in terms of the existence of two topological redox isomers: a weakly boundary-associated Mn(salen) complex, whose electrochemical response corresponds to a reversible one-electron transfer controlled by diffusion of the positive ions of the supporting electrolyte through the zeolite surface windows and channels, and a…
Electrochemical conversion of pressurized CO2 at simple silver-based cathodes in undivided cells: study of the effect of pressure and other operative…
2020
Abstract Electrochemical reduction of pressurized CO2 is proposed as an interesting approach to overcome the main hurdle of the CO2 electrochemical conversion in aqueous solution, its low solubility (ca. 0.033 M), and to achieve good faradaic efficiency in CO using simple sheet silver cathodes and undivided cells, thus lowering the overall costs of the process. The effect on the process of CO2 pressure (1–30 bar), current density, nature of the supporting electrolyte and other operative conditions, such as the surface of the cathode or the mixing rate, was studied to enhance the production of CO. It was shown that pressurized conditions allow to improve drastically the current efficiency o…
Influence of chloride anions on the electrodeposition and electroactivity of the polymer matrix in polypyrrole, poly( N -methylpyrrole) and polypyrro…
2004
We report electrochemical studies on the influence of a small concentration of chloride ions on the electroactivity of the polymer matrix of polypyrrole (PPy), poly(N-methylpyrrole) [p(N-MePy)] and a poly(titanocene-propyl-pyrrole) derivative, p(Tc3Py) [Tc(CH2)3NC4H4; Tc=CpCp′TiCl2; Cp=C5H5; Cp′=C5H4] in acetonitrile (AN), tetrahydrofuran (THF) and N,N-dimethylformamide (DMF). The polymer films were obtained on Pt disc electrodes from AN solutions of the monomers containing 0.1 M tetrabutylammonium hexafluorophosphate (TBAPF6) as the supporting electrolyte and then transferred to the corresponding monomer-free solution. Studies in Cl−-containing solutions have shown that the p(Tc3Py) matrix…
Uranium(VI) sequestration by polyacrylic and fulvic acids in aqueous solution
2011
Stability data on the formation of dioxouranium(VI) species with polyacrylic (PAA) and fulvic acids (FA) are reported with the aim to define quantitatively the sequestering capacity of these high molecular weight synthetic and naturally occurring ligands toward uranium(VI), in aqueous solution. Investigations were carried out at t = 25 °C in NaCl medium at different ionic strengths and in absence of supporting electrolyte for uranyl–fulvate (\( {{\text{UO}}_{2}}^{2+} \)–FA) and uranyl–polyacrylate (\( {{\text{UO}}_{ 2}}^{ 2+ } \)–PAA, PAA MW 2 kDa) systems, respectively. The experimental data are consistent with the following speciation models for the two systems investigated: (i) UO2(FA1),…
Impedance investigation of BaCe0.85Y0.15O3-delta properties for hydrogen conductor in fuel cells
2012
International audience; The influence of the sintering conditions on the electrochemical properties of the proton conducting electrolyte BaCe0.85Y0.15O3-delta (BCY15) and Ni - based BCY15 cermet anode for application in high temperature proton conducting fuel cell are investigated by electrochemical impedance spectroscopy. The results show that at lower sintering temperatures due to the formation of parasitic Y2O3 phase an increase of both the electrolyte and electrode resistances is observed. This effect is strongly reduced by enhancement of the sintering temperature. The obtained BCY15 conductivity (sigma = 2.5x10(-2) S/cm at 700 degrees C) is comparable with that of the best proton condu…
Electroosmotic effects in the determination of ion mobilities of carrier-free radionuclides in free aqueous electrolyte solutions
2001
A device for on-line electromigration studies of radio-elements in free electrolytes has been tested by measuring the absolute individual ion mobilities of no-carrier-added single charged anions [99mTc]TcO4 - and [18F]F- and differently charged cations [137Cs]Cs+, [57Co]Co2+ and [241Am]Am3+ in inert aqueous electrolytes at 298.1 K. The observed ion mobilities were found to be influenced by electroosmosis in the migration tube. A relation to correct this effect is proposed. In addition, it was shown that the effect of electroosmosis may be suppressed by chemical treatment of the surface of the migration tube.
Electrosynthesis of Ce–Co Mixed Oxide Nanotubes with High Aspect Ratio and Tunable Composition
2008
Cerium oxide and cobalt oxides have attracted the interest of several researchers due to their potential application in several technological fields electrochromism, lithium batteries, catalysis, etc.. Ceria has been used as a promoter in the so-called “three-way catalyst” for the control of toxic emission from automobile exhaust. The promotion consists of the enhancement of the noble metal dispersion, as well as stabilization of the supporting medium toward thermal sintering. 1,2 A direct catalytic effect of CeO2 in chemical processes such as water–gas shift reaction or NOx decomposition has been also evidenced. 3,4