In this study, Nd_1.6Ca_0.4Ni_1−yCu_yO_4+δ-based electrode materials for intermediate temperature solid oxide fuel cells (IT-SOFCs) are investigated. Materials of the series (y = 0–0.4) are obtained by pyrolysis of glycerol-nitrate compositions. The study of crystal structure and high-temperature stability in air and under low oxygen partial pressure atmospheres are performed using high-resolution neutron and in situ X-ray powder diffraction. All the samples under the study assume a structure with Bmab sp.gr. below 350 °C and with I4/mmm sp.gr. above 500 °C. A transition in the volume thermal expansion coefficient values from 7.8–9.3 to 9.1–12.0 × 10⁻⁶, K⁻¹ is observed at approximately 400 °C in air and 500 °C in helium.The oxygen self-diffusion coefficient values, obtained using isotope exchange, monotonically decrease with the Cu content increasing, while concentration dependence of the charge carriers goes through the maximum at x = 0.2. The Nd_1.6Ca_0.4Ni_0.8Cu_0.2O_4+δ electrode materialdemonstrates chemical compatibility and superior electrochemical performance in the symmetrical cells with Ce_0.8Sm_0.2O_1.9, BaCe_0.8Sm_0.2O_3−δ, BaCe_0.8Gd_0.19Cu_0.1O_3−δ and BaCe_0.5Zr_0.3Y_0.1Yb_0.1O_3−δ solid electrolytes, potentially for application in IT-SOFCs.

This work presents the results from a study of the structure and transport properties of Ca-doped La₂NiO_4+δ. La_2−xCa_xNiO_4+δ (x = 0–0.4) materials that were synthesized via combustion of organic-nitrate precursors and characterized by X-ray diffraction (XRD), in situ XRD using synchrotron radiation, thermogravimetric analysis (TGA) and isotope exchange of oxygen with C¹⁸O₂. The structure was defined as orthorhombic (Fmmm) for x = 0 and tetragonal (I4/mmm) for x = 0.1–0.4. Changes that occurred in the unit cell parameters and volume as the temperature changed during heating were shown to be caused by the excess oxygen loss. Typical for Ruddlesden–Popper phases, oxygen mobility and surface reactivity decreased as the Ca content was increased due to a reduction in the over-stoichiometric oxygen content with the exception of x = 0.1. This composition demonstrated its superior oxygen transport properties compared to La₂NiO_4+δ due to the enhanced oxygen mobility caused by structural features. Electrochemical data obtained showed relatively low polarization resistance for the electrodes with a low Ca content, which correlates well with oxygen transport properties.

In this work, we studied the structural features of La_1.9Ca_0.1NiO_4.11, which is considered a promising cathode material for intermediate temperature solid-oxide fuel cells (IT-SOFC). The effect of different pretreatments on the structural characteristics of the sample was studied using X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) in order to elucidate the origin of a peculiar change of lattice parameters observed earlier during in situ XRD studies. The XRD studies have shown that anisotropic broadening for reflections with a high Miller index l appears after tempering of a quenched (from 1100 °C) sample at 250 °C. This temperature is too low for the release/incorporation of oxygen into the structure but is sufficient for oxygen migration inside the structure. The HRTEM assisted us in revealing differences in the defect structure after different pretreatments. Based on obtained results, the following possible explanation was proposed. Observed additional microstrains and non-oriented planar defects as well as a decrease in the coherent scattering region size in the [00l] direction are caused by the non-homogeneous redistribution of interstitial oxygen in the structure during tempering.

Graphitic carbon nitride g-C₃N₄ has been modified using platinum and platinum oxide (0.5–5 wt.%) and studied in photocatalytic H₂ evolution reactions with ethanol aqueous solution under visible light irradiation (λ = 409 nm). An analysis of the by-products of the reaction (CO₂, CH₄, C₂H₆ etc.) was also carried out. The morphology, particle size distribution, and optical properties of the photocatalysts, and the chemical states of platinum cations were examined using various methods. The photocatalysts were investigated using a wide range of methods to clarify the morphology, particle size distribution, optical properties, and the chemical states of platinum cations. Factors affecting not only the activity, but also the selectivity of the photocatalyst in the target process of hydrogen production, have been established. The highest rate of H₂ evolution achieved over 0.5 wt.% Pt/g-C₃N₄ photocatalyst is 0.6 mmol h⁻¹ g⁻¹ (selectivity 98.9%), which exceeds the activity of pristine g-C₃N₄ by 250 times. Increasing the Pt or PtO content up to 5 wt.% leads to an increase in the rate of formation of by-products (CH₄, C₂H₆, and CO₂) and a decrease in the selectivity of H₂ evolution. The study also delves into the role of platinum and the mechanism of charge transfer in PtO/g-C₃N₄ and Pt/g-C₃N₄ photocatalysts due to light irradiation.