Vol 54, No 2 (2018)

Four new ion-selective electrodes (ISEs) based on poly-(1-4)-2-amino-2-deoxy-β-D-glucan (chitosan) ionophore were constructed for determination of uranyl ion (UO₂(II)) over wide concentration ranges. The linear concentration range for carbon paste electrodes (CPEs) was 1 × 10^–6–1 × 10^–2 mol/L with a detection limit of 1 × 10^–6 mol/L and that for the screen-printed electrode (SPEs) was 1 × 10^–5–1 × 10^–1 mol/L with a detection limit of 8 × 10^–6 mol/L. The slopes of the calibration graphs were 29.90 ± 0.40 and 29.10 ± 0.60 mV/decade for CPEs with dibutylphthalate (DBP) (electrode I) and o-nitrophenyloctylether (o-NPOE) (electrode II) as plasticizers, respectively. Also, the SPEs showed good potentiometric slopes of 29.70 ± 0.30 and 28.20 ± 1.20 mV/decade with DBP (electrode III) and o-NPOE (electrode IV), respectively. The electrodes showed stable and reproducible potential over a period of 54, 62, 101 and 115 days for electrodes I, II, III, and IV, respectively. The electrodes manifested advantages of low resistance, very fast response and, most importantly, good selectivities relative to a wide variety of other cations except Ce(III) ion which interfere seriously. The results obtained compared well with those obtained using atomic absorption spectrometry.

State-of-the-art in the studies of sodium-ion batteries is discussed in comparison with their deeper developed lithium-ion analogs. The principal problem hindering the development of competitive sodium-ion batteries is the low effectiveness of the electrode materials at hand. The principal efforts in the formation of anodes for the sodium-ion batteries are reduced to the development of materials based on carbon, metals, alloys, and transition metal oxides. Cathode materials are searched among oxides (first of all, layered) and salt systems. Synthesis of electrolytes for the sodium-ion batteries is not sufficiently attended to. Nowadays it is sodium salt solutions in organic solvents that are dominated; however, polymer and solid electrolytes with sodium conductivity may be thought of as very perspective. Reference list contains 584 items.

Conditions of the chemical solution deposition of CaZrO₃-based electrolyte films on supporting composite electrodes are studied. The films are formed on the composites of CaZrO3 with metal oxides СuO, Fe₂O₃, and NiO. The morphology and the phase and elemental composition of supports and films are studied as well as the gas permeability and conductivity of films. It is concluded that composites of calcium zirconate with nickel can be recommended as the supporting anodes for the proton-conducting CaZr_0.9Y_0.1O_3–δ film electrolyte.

The reduction of the bromate anion on a rotating disk electrode (RDE) in a steady-state mode due to the catalytic cycle consisting of a reversible bromine/bromide redox pair and irreversible counter-proportionation reaction was studied theoretically. As the cycle is autocatalytic (EC″ mechanism: Electrochim. Acta, 2015, vol. 173, p. 779), at high volume concentrations of bromate the passing current can reach huge values limited by the ultimate diffusion current of bromate through the diffusion layer even at very low volume concentrations of bromine. In contrast to previous theoretical studies of this process, for numerical solution of the set of nonlinear equations with boundary conditions for concentrations we used the COMSOL Multiphysics program package, with which the solution can be found for both the galvanostatic mode (at a given current density) and the maximum current density. This allowed us to study the behavior of the maximum current density for the case of very high thickness of the diffusion layer and very high reaction rate constant. In this mode, the ratio of the maximum current to the limiting diffusion current of the reduction of the bromate anion to bromine was found to exceed not only intuitively anticipated unity, but also the “critical” value of 1.2, which formally corresponds to the limiting diffusion current of its reduction to the bromide anion (though the real end product is bromine), and this limiting value depends on the volume concentrations of both bromate and bromine.