Russian Journal of Electrochemistry最新文献

A series of planar billets of NiO/Ce_0.8Gd_0.2O₂ (NiO/GDC) anodes for solid oxide fuel cells are fabricated by the method of microdrop 3D printing using a pneumatic dispenser. The porosity and the coefficient of sintering-induced shrinkage of anode billets are studied as a function of their preparation method. The anode billets are reduced to obtain Ni/Ce_0.8Gd_0.2O₂ cermet and the thus obtained samples are studied as regards the effect of printing parameters on their morphology and structure. It is shown that the use of 3D printing increases the porosity of the Ni/GDC composite from 7 to 23% as compared with the casted samples, on retention of the high conductivity of (2.82 ± 0.06) × 10³ S/cm.

The structural characteristics of loose zinc deposits obtained in pulse-potential modes are calculated using a phenomenological model. Increasing the duty cycle leads to intensified anodic dissolution during pauses and obtaining of denser deposits, due to the formation of dendrites with fewer tips, yet, a larger diameter as compared to the deposits obtained in the potentiostatic mode. The linear dependence of the diameter of the tips of dendrites forming a loose zinc deposit on the duty cycle is found. There is a critical time corresponding to the achievement of zero deposit growth rate when the metal deposited during the pulse will completely dissolve during the pause.

Results of high-temperature oxygen desorption from SrCoO_{3 – δ}-oxide with mixed conductivity composed of obtained using an original quasi-equilibrium oxygen release technique are shown. The measurements are carried out with a characterized powder sample in a tubular reactor. The equilibrium phase diagram of the oxide in the 600–850°C temperature range and partial pressure of oxygen 0.2–6 × 10^–5 atm is constructed. With the help of literature data, a correlation of phase diagram regions with their corresponding structures is obtained.

The electrochemical properties of [Co(Ph₂PCH₂P(Ph)₂PPPPP(Ph)₂CH₂PPh₂)]BF₄ complex have been studied by the method of cyclic voltammetry. The electrochemical methylation of this complex have been cunducted in the presence of iodomethane which has led to the formation of phosphonium salt—methylene bis(methyldiphenylphosphonium) diiodide as final product. It was found, that this reaction proceeds with the breakage of the P–P bonds in polyphosphorus ligand and with the formation of new P–C bonds.

This work is devoted to the study of thermodynamic characteristics and phase stability of oxides with a perovskite structure using both classical and original methods for the studying of compounds with similar composition. An oxide with mixed oxygen–electronic conductivity La_0.6Sr_0.4MnO_{3 – δ} obtained by solid-state synthesis was chosen as object of research. The stoichiometric range of this composition has been established at temperatures of 600–900°C in the region of oxygen partial pressure up to 3 × 10^–4 atm. The chemical potential of oxygen in the gas phase is calculated, as well as the dependences of the oxygen partial molar enthalpy and entropy in the oxide in the nonstoichiometry range δ = 0.01–0.012.

Composite solid electrolytes based on n-methyl-n-butylpiperidinium tetrafluoroborate [(CH₃)(C₄H₉)C₅H₁₀N]BF₄–A (where A is γ-Al₂O₃, SiO₂) were synthesized, and their thermal and electrically conductive properties were studied. The conductivity of the (1 – x)[C₁₀H₂₂N]BF₄–xAl₂O₃ composites passes through a maximum at x ~ 0.9, reaching 4.6 × 10^–4 S/cm at 130°C for 0.1[C₁₀H₂₂N]BF₄–0.9Al₂O₃. The absence of a thermal effect at the melting temperature of the ionic salt, showing high ionic conductivity, indicates that at x ≥ 0.9 n-methyl-n-butylpiperidinium tetrafluoroborate is in the amorphous state, and ion transport occurs along the ionic salt/oxide interface. In the case of the [C₁₀H₂₂N]BF₄–SiO₂ composites, the effect of a heterogeneous dopant on the ion transport is less significant, and the conductivity is due to the ionic salt of the additive present in the pores.

At the electrochemical deposition of alloys various phenomena are observed that lead to changes in the kinetics and thermodynamics of the processes. In particular, as a result of changing in the nature of the electrode surface, both the exchange current densities and the transfer coefficients of each of the components changed. Further, during the formation of solid solutions, the equilibrium potentials of the components change due to the non-zero enthalpy and entropy of mixing. At the deposition of eutectic-type alloys (that is, a mixture of grains of individual components), each of the metals does not deposit on the entire electrode surface but only on its own surface. In the latter case, there is a change in the diffusion pattern of the components as compared to the deposition of individual metals: it remains unchanged in the outer part of the diffusion layer but there is a condensation of the diffusion fields of the components near the surface, similar to the case of diffusion to the matrix of microelectrodes or to individual nuclei of a new phase. This also leads to a change in the diffusion part of the overpotential of the components’ deposition. The diffusion of ions of the discharging negative component of an alloy representing a mechanical mixture of the metals’ A and B grains to the grain surface of this component in the model of a partially blocked electrode is considered. At a constant potential, the local current density of the component is shown to increase as a result of the diffusion acceleration. The magnitude of the relative increase in the current and the corresponding magnitude of apparent depolarization are found, as compared between the deposition of an individual metal and the codeposition of the same component into an alloy.

A citrate–nitrate synthesis of individual materials La_0.9Sr_0.1Sc_{1 – x}Co_xO_{3 – δ} and La_0.9Sr_0.1CoO_{3 – δ} and their based composites is performed. Composite materials are obtained by solid-phase mixing in different percentages of individual phases, followed by pressing and sintering. The obtained individual and composite materials are explored by X-ray phase analysis and dilatometry. The electrical conductivity of the obtained samples is studied by a direct-current four-probe method depending on the temperature and the gas phase composition. Unique studies of the ability of composites to the ammonia direct decomposition directly at the electrode layer of the fuel cell are carried out.