Vol 53, No 2 (2017)

The effect of the water-repellent agent and carbon nanotubes introduced in the porous cathode of an oxygen–hydrogen fuel cell on the porous structure and electrochemical characteristics of the cell was studied by chronoamperometry, adsorption structural analysis, electron microscopy, and gravimetric analysis.

The specific adsorption of bromide and iodide ions from mixed solutions [0.1 m M LiBr + 0.1 (1 – m) M LiBF₄] and [0.1 m M LiI + 0.1 (1 – m)M LiBF₄] in dimetylformamide (DMF) with the following fractures m of surface-active anion: 0, 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, and 1 is studied on a renewable liquid (Cd–Ga) electrode by means of an ac bridge. The data on the specific adsorption of Br^– and I^– anions can be quantitatively described by the Frumkin isotherm, the same as the data on Cl^–. It is found that in contrast to Hg/DMF and Bi/DMF interfaces for which the adsorption energy of halide (Hal^–) anions (ΔG_ads) increases with the transition from Cl^– to Br^– and further to I^–, on the (Cd–Ga)/DMF interface, the ΔG_ads values increase in the inverted sequence I^–< Br^–< Cl^–. It is found that the energy of (Cd–Ga) interaction with Hal^– anions (\(\Delta {G_{\left( {{\text{Cd - Ga}}} \right) - Ha{l^ - }}}\)) also increases in the sequence I^– < Br^– < Cl^–. The comparative analysis of the results on the Hal^– adsorption on the (Сd–Gа)/DMF and (In–Gа)/DNF interfaces shows that the interaction energies metal–DMF and metal–Hal^– correlate with one another. For (Cd–Ga) and (In–Ga) electrodes which have virtually the same energy of metal–DMF interaction, the corresponding values of \(\Delta {G_{\left( {{\text{Cd - Ga}}} \right) - Ha{l^ - }}}\) and \(\Delta {G_{\left( {{\text{In - Ga}}} \right) - Ha{l^ - }}}\) turn out to be close not only for Cl^– but also for Br^– and I^–.

In this work, cyclic voltammetry (CV) and chronoamperometry (CA) were used to study the electrodeposition mechanism of red selenium on platinum and (ITO) substrates from aqueous solution containing (SeO₂) and sodium citrate as support electrolyte with pH 4.3 at ambient temperature. The potentiostatic current transients were analyzed according to Scharifker–Hills model. The morphological characterization of the deposit was carried out by Scanning Electron Microscopy (SEM), whereas the optical one was realized by UV-Visible spectroscopy. The results shown that the nucleation mechanism of Se on each substrate is instantaneous with a three-dimensional growth of the hemispherical nuclei. The nucleation density (N₀) is exponentially increased with the applied overpotential. Se thin film has an energy gap of about 2.4 eV.

Lanthanum–strontium gallate–ferrites are thought of as perspective electrode materials. A series of La_{1 –x}Sr_xFe_{1 –y}Ga_yO_{3 – δ} (x = 0.2–0.5; y = 0–0.4) compositions is synthesized by self-propagating high-temperature synthesis. The solid solutions’ existence domain is identified. The linear expansion thermal coefficient and the electric conductivity of the materials in the form of ceramics are studied for single-phase samples.

The application of gold nanoparticles (AuNPs) modified glassy carbon electrode in the electrochemical detection of arsenic is presented. AuNPs were electrodeposited onto the surface of a glassy carbon electrode (GCE) by cyclic voltammetry in a potential range of–400 to 1100 mV for 10 cycles. The modification of the GCE with AuNPs resulted in increased redox current of [Fe(CN)₆]^3–/4– when compared to that obtained from bare GCE. As(III) detection was carried out using square wave anodic stripping voltammetry (SWASV) at the following optimised conditions: pH 1, deposition potential of–600 mV and pre-concentration time of 60 s. The GCE–AuNPs electrode detected As(III) to the limit of 0.28 ppb and was not susceptible to many interfering cations except Cd, Cu and Hg. The GCE–AuNPs electrode was used for the quantitative analysis of arsenic in real water sample. The results obtained were in good correlation with those obtained from inductively coupled plasma—optical emission spectroscopy technique, thus validating the reported method.

The work is devoted to the study of transport properties at the SrMoO₄/MoO₃ interface and examination of composite phases based on these compounds. The mass transfer in the (‒)MoO₃/SrMoO₄/MoO₃(+) cell is studied in the spontaneous mode (with no polarization) and electric field-induced mode. In the spontaneous mode, MoO₃ is drawn onto the inner surface of SrMoO₄ ceramic briquette. Under a polarization, molybdenyl ion {MoO₂}²⁺ is one of the charge carriers, which is evidenced by the Tubandt method. Thus, both spontaneously and under an external polarization, MoO₃ is transferred onto the inner surface of SrMoO₄ ceramics. It is found that the ionic transfer prevails for SrMoO₄: the average transport numbers by the emf method are close to unity, the oxygen activity in the gas phase (in the range 0.21…10^–5 atm) has no effect on the conductivity. The composites {SrMoO₄–xMoO₃} (where x = 1, 5, 10, 15, 20 mol %) are fabricated; the presence of two phases is evidenced by the X-ray diffraction analysis. The temperature dependence of the total conductivity is determined. In the range of small MoO₃ additions to SrMoO₄, the conductivity steeply increases revealing the similarity to the {MeWO₄–xWO₃ (Me–Ca, Sr, Ba)} composites.

A procedure has been developed for electrochemical polymerization of dianiline dichlorobenzoquinone and electrosynthesis of a composite material based on poly(dianiline dichlorobenzoquinone) and multiwalled carbon nanotubes (MCNTs) in 1 M H₂SO₄. The introduction of a polymerization initiator (potassium hexachloroiridate IrCl₆²⁻ (HCI)) accelerated the growth of the electrode coating. The introduction of MCNTs led to the creation of a current-conducting framework in the composite and an increase in the mass and electrochemical capacity of the electrode coating. The electrochemical behavior of the composite is similar to that of polyaniline (PAni), but includes the redox reaction of the chloranil substituents. The charging of the double electric layer makes a significant contribution to the electrochemical capacity.