Vol 52, No 8 (2016)

The kinetics of interaction of gas-phase oxygen with oxygen of perovskite-like manganites La_{1 - x}A_xMnO_{3 ± δ} (A = Ca, Sr, Ba) at a temperature of 850°C and an oxygen pressure of 1 kPa was studied by isotope exchange of oxygen with analysis of the gas phase. The rates of the interphase exchange, dissociative adsorption, and incorporation of oxygen in the crystal lattice of perovskites La_0.7A_0.3MnO_{3 ± δ} (A = Ca, Sr, Ba) and La_1–xSr_xMnO_{3 ± δ} (x = 0, 0.3, 0.4) were calculated. The dissociative adsorption of oxygen was found to be the limiting stage of the exchange. The influence of the defective structure of oxide La_{1 - x}A_xMnO_{3 ± δ} on the mechanism of exchange with oxygen of the gas phase was discussed.

After the deposition of Pt on their surface, the carbon nanofiber materials synthesized by sequential oxidation and pyrolysis of electrospun nanofiber mats based on polyacrylonitrile are used as the gas-diffusion electrodes for high-temperature hydrogen–air fuel cells on a polybenzimidazole (PBI) proton-conducting membranes. In contrast to the traditional methods of electrode preparation in which the catalyst (Pt) nanoparticles are localized on the surface of carbon black which is applied as “ink” on the conducting support (carbon paper or tissue), in this study the Pt nanoparticles are being deposited and developed on the surface carbon nanofibers to form a combined gas-diffusion material. In the tests, the resulting electrodes demonstrate good efficiency within hydrogen-air fuel cells on the PBI membrane.

A new complex of aniline (An) with tetracyanoquinodimethane (TCQM) An(TCQM)₄ has been obtained and studied. The redox cycling of polyaniline (PAni-sulfo) in a neutral electrolyte containing Cl^– and ClO₄⁻ anions led to a replacement of the sulfate anion by the Cl^– and ClO₄⁻ anions. The TCQM anion can also replace the sulfate anions in polyaniline (PAni) during the cycling of the latter in a neutral electrolyte containing TCQM anions. The introduction of TCQM in PAni creates conditions for generating nanocrystalline regions inside the polymer.

The electric capacity of electrochemical capacitors with composite electrodes obtained by laser microstructuring was studied. The obtained electrodes allowed control of the contribution of the resistance of the electrode material and electrolyte to the total equivalent series resistance of the electrochemical capacitor. This allowed us to determine their effect on the resulting characteristics of the capacitors. The dependences of the specific electric capacity on the parameters of the composite structure of electrodes were studied, and the optimum parameters were found.

A new member of the polyporphine series—cobalt polyporphine of type I (pCoP-I)—was prepared from the starting magnesium polyporphine of type I (pMgP-I) by ion exchange, i.e. by sequential processing of the pMgP-I polymer film on the electrode surface with solutions of trifluoroacetic acid (forming metalfree polyporphine of type I, pH₂P-I) and cobalt(II) acetate in organic solvents. The completeness of each stage of ion exchange can be judged from the change in the electrochemical and spectral characteristics of the obtained polymer films of unsubstituted porphine (?H2P-I) and cobalt porphine (pCoP-I) of type I. Oxidative transformation of this polyporphine pCoP-I was performed, which led to the formation of additional bonds between the neighboring porphine units in the polymer film (transition of polymer of type I into polymer of type II, pCoP-II). The behavior of the polymer films of cobalt polyporphine of types I and II in oxygen electroreduction was studied. The films showed catalytic activity in this process.

The earlier obtained data on the transport properties of cesium-conducting solid electrolytes based on cesium orthophosphate in the Cs_3–2xM_x^II PO₄ (M^II = Mg, Ca, Sr, Ba), Cs_3–3x PO₄ (M_x^III = Sc, Y, La, Sm, Nd) and Cs_3–xP_1–xZ_x^VI O₄ (Z = S, Cr, Mo, W) systems are analyzed. It is shown that, in addition to the conventional jump mechanism, the “paddle wheel” mechanism can play an important role in the ionic transport. This mechanism is associated with the orientation disordering of [PO₄] tetrahedrons at the elevated temperatures, which leads to their rotation promoting “pushing” cesium ions into the accessible neighboring positions.