Transport of ionic charge and solvent in poly(3-octylthiophene) films: An electrochemical quartz crystal microbalance study

The results of a study of poly(3-octylthiophene) films with the aid of an electrochemical quartz microbalance are presented. The effect of the nature of the electrolyte anion on the determined weights of mobile species that are transported through the film/electrolyte interface is discussed. The obtained results point to a substantial role played by the solvent transport in the course of the electrode reaction. The results concerning the influence exerted by the electrode material on the observed regularities are presented.     

Double-Layer Effects in the Electroreduction of Cobalt(III) Trioxalate Complexes to Cobalt(0) Atoms on a Dropping Mercury Electrode

A polarographic investigation of solutions containing trioxalate complexes of Co(III) reveals that the overall electrode process Co(III) Co(0) is accompanied by slow formation of ionic associates between aquacomplexes of Co(II) and trioxalate complexes of Co(III). Use of a relatively high concentration of oxalate ions (0.001 M) quells this association. Under these conditions, it is possible to divide the measured current into two constituents related to the primary electroreduction Co(III) Co(II) and the subsequent process Co(II) Co(0). The earlier data on the rate constant and apparent transfer coefficient for the process Co(II) Co(0) are used for calculating corrected Tafel plots for the electrode reaction Co(III) Co(II). The plots are practically linear and independent of the concentration of the supporting-electrolyte cation in a wide range of potential drops (1 V) across the dense layer. A theoretically expected parallel shift of the plots is observed in solutions with a variable concentration of discharging species. This observation and similar data obtained for a mixed potassium–sodium supporting electrolyte bear testimony to good agreement between the obtained results and the theory.     

Cyclic Voltammetry and the Impedance of Electrodes Modified by Indium(III) Hexacyanoferrate Films

The results of studying indium(III) hexacyanoferrate films by the cyclic voltammetry and faradaic impedance methods are presented. It is shown that the synthesis from solutions with different contents of potassium salts leads to the appearance of films with different electrochemical properties. The impedance spectra exhibit semicircles corresponding to the Randles circuit and portions of the Warburg dependence. Parameters of the equivalent circuit corresponding to the obtained spectra are determined.     

Thermodynamic properties of solutions in the system <Emphasis Type="Italic">o</Emphasis>-xylene–di-2(ethylhexyl)phosphoric acid

The saturated vapor pressure in the temperature range of 298.15–308.15 K and the density of solutions in the o-xylene–di-2(ethylhexyl)phosphoric acid system at 298.15 K are measured. The activity coefficients of o-xylene in the above temperature range are calculated on the basis of the resulting data. The parameters of the thermodynamic model UNIQUAC are determined and analytical relationships are proposed to describe the bulk properties of the solution.     

Impedance of Indium(III) Hexacyanoferrate Films: Effect of the Supporting-Electrolyte Cation

Films of indium(III) hexacyanoferrate are studied in nitrate solutions of lithium, sodium, potassium, and ammonium using cyclic voltammetry and faradaic impedance. Effect of the supporting-electrolyte cation on parameters of the equivalent circuit corresponding to the impedance spectra is analyzed. The charge transport at the electrode/film interface is shown to be slow. The cation bonding in a film is discussed.     

Electron absorption spectra and voltabsorptograms of poly-3-octylthiophene films

Steady-state absorption spectra of poly-3-octylthiophene films in different oxidation states and differential cyclic voltabsorptograms of poly-3-octylthiophene films in 0.1 M LiClO₄ solutions in acetonitrile are studied. Electron spectra of films demonstrate the following three absorption bands: a complex band with a pronounced maximum at λ = 450 nm, which corresponds to π → π* electron transitions in the reduced fragments of poly-3-octylthiophene films and two absorption bands (at λ_max = 780 and λ_max > 1100 nm), which correspond to the oxidized film fragments. It is concluded that two chemically and optically distinguishable oxidation products are formed during the polymer oxidation.     

Redox polymer poly-N,N′-2,3-dimethylbutane-2,3-diyl-bis(salicylideniminato)nickel: An impedance spectroscopy study

Films of poly-N,N-2,3-dimethylbutane-2,3-diyl-bis(salicylideniminato)nickel are studied by cyclic voltammetry and faradaic impedance methods in acetonitrile solutions containing 0.1 M tetraethylammonium tetrafluoroborate. The resistance to charge transfer and the double-layer capacitance, calculated from the semicircle in the high-frequency spectrum portion, are referred to the film/electrolyte interface. From the low- and mid-frequency impedance spectra portions, the low-frequency capacitance and the effective diffusion coefficient of charge carriers are determined. The assumption about a noticeable film porosity is shored up by direct scanning electron microscopy examination of film surfaces.__________Translated from Elektrokhimiya, Vol. 41, No. 4, 2005, pp. 433–441.Original Russian Text Copyright © 2005 by Dmitrieva, Logvinov, Kurdakova, Kondratev, Malev, Timonov.