Hexagonal perovskites with intergrowth structure are novel and promising class of protonic conductors. The development of this class of materials makes it possible to develop proton-conducting materials for intermediate temperatures (300-600 degrees C) electrochemical devices including fuel cells. In this work, non-metal doping strategy was first applied to this class of materials. New hexagonal perovskite Ba7In6Al1.9P0.1O19.1 was obtained and investigated as a proton conductor. Ba7In6Al1.9P0.1O19.1 showed the ability to water uptake and exhibited significantly higher values of hydration degree (1.31 mol H2O), than parent compound (0.41 mol H2O). The high hydration ability is explained by the increase in the unit cell volume, and, consequently, the increase in sufficient space for the incorporation of OH- -groups in hexagonal layer. The investigation of transport properties showed that in dry atmosphere (pH(2)O = 3.5.10(-5) atm) the Ba7I-n(6)Al(1.9)P(0.1)O(19.1) compound was a mixed conductor. Doping made it possible to increase the oxygen-ion conductivity by 0.25 orders of magnitude. In wet air (pH(2)O = 2.10(-2) atm) below similar to 500 degrees C the conductivity was the predominantly protonic. Proton conductivity increased by 0.5 orders of magnitude compared to the undoped phase as a result of the increase in proton concentration. Thus, investigated phase Ba7In6Al1.9P0.1O19.1 is a promising electrolyte for intermediate-temperature electrochemical devices. The strategy of phosphate oxyanion doping is a successful method for optimizing transport properties of hexagonal perovskite with intergrowth structure.

The thermal and electric properties of the Y3+-doped Ba7In5.9Y0.1Al2O19 phase with the hexagonal perovskite structure (a = 5.935(7) Å, c = 37.736(8) Å) are studied. It is shown that this phase can incorporate protons and exhibit protonic conduction. Upon addition of an isovalent dopant, yttrium, the concentration of protons increases (up to the limiting value for Ba7In5.9Y0.1Al2O19·0.55H2O), as a result of the increase in the unit cell volume and, correspondingly, in the free space for accommodating OH– groups in the oxygen-deficient block containing coordination-unsaturated polyhedrons [BaO9]. The isovalent doping increases the oxygen-ionic conductivity due to an increase in interatomic distances and a decrease in the activation energy of migration. In a humid atmosphere (pH2O = 1.92 × 10−2 atm), the Ba7In5.9Y0.1Al2O19 phase exhibits the higher values of protonic conductivity as compared with the matrix compound Ba7In6Al2O19 and below 500°C is characterized by the predominant proton transport both in air and in a wide pO2 region (10–18–0.21 atm).

The mass-transfer of oxygen and hydrogen between the gas phase containing humidified O2 and the La n+1Ni n O3n+1 (n = 1, 2, 3) electrode in contact with the proton-conducting La28-z W4+z O54+1.5z (LWO) electrolyte has been studied. The measurements were performed using the 18O pulse isotope exchange (PIE) technique in the temperature range of 350-800 degrees C under a flow of He + O2 in both dry and humid conditions. Electrochemical studies were carried out using electrochemical impedance spectroscopy (EIS) within the temperature range of 600-800 degrees C in humid air. The PIE study demonstrated that all La n+1Ni n O3n+1 oxides exhibit oxygen surface exchange with O2 and H2O, and the results were further justified by 1H NMR and TGA studies. The mechanism of oxygen surface exchange is discussed. EIS measurements revealed two distinct surface exchange processes for the La3Ni2O7-delta and La4Ni3O10-delta electrodes in contact with LWO, which is explained by the two-step mechanism proposed on the basis of the PIE studies. The EIS and PIE results showed that the hydration of La4Ni3O10-delta occurs through the interaction of oxygen with water on the electrode surface in a humid atmosphere, leading to the formation of hydroxyl groups and their subsequent incorporation into structural oxygen vacancies.

Proton-conducting oxide electrolytes can be used in protonic ceramic electrochemical cells (PCECs) applied for power generation and sustainable hydrogen production (Norby, 2001) [1]. For successful using PCECs, their long-term stability and high performance characteristics are required, accordingly, protonic electrolyte must have a wide range of functional characteristics (Hossain et al., 2017) [2]. Besides, the lowering the PCECs operating temperature can facilitate their scale-up and commercialization. However, achieving high proton conductivity at low operating temperatures is a long-standing challenge. Here, for the first time, we show the discovering a high proton conduction with low activation energy in hexagonal perovskite Ba7Sc6Al2O19 with cation- and oxygen-deficient layers. The sample shows high bulk proton conductivity of similar to 5.10(-3) S cm(-1) at 300-500 degrees C with very low activation energy 0.12 eV, and high chemical stability (towards to H-2, CO2 and electrode materials). These results demonstrate that new super-protonic Ba7Sc6Al2O19 is a promising proton conductor for the applications both in intermediate and low-temperature (<400 degrees C) solid-oxide fuel cells.

Populations of the Colorado potato beetle exhibit by a high level of polymorphism, which enables them to have high ecological plasticity and quickly adapt to various conditions. Our research examines the variability of the pattern of the central part of the pronotum of the Colorado potato beetle Leptinotarsa decemlineata in samples collected from two localities of the Middle Urals over several years. New variants of the pattern are described, which have not been previously observed in the European part of the Russian Federation. Higher degree of melanization is typical for these variations. Furthermore, these variants are characterized by the merging of the central stripes with each other and with the lower spot. In the populations of the Middle Urals, variants 1–3 dominated with a cumulative frequency of occurrence of 32–55 %; and a new variant a was found in significant quantities (5–12 %). In total, the frequency of newly registered variants with increased melanization was 17–36 %. A well-expressed long-term variability in the frequencies of variants of the pronotum pattern was discovered, associated with a gradual increase in the frequency of occurrence of mass variants 1–3. Synchronously in both localities, a sharp increase up to 18–20 % was recorded in the frequency of variant 9 in 1998. Overall, synchronous samples were more similar to each other than to samples from the same localities in other years. The synchronous temporal dynamics of variant color frequencies may prove that these settlements belong to one large population of the Colorado potato beetle. In general, the obtained results indicate the ongoing processes of population structure formation of the species in the new distribution area, specifically in the territory of the Middle Urals.

The Ba3InGa2O7.5 complex oxide, possessing the perovskite-related structure with structural oxygen vacancies, was first synthesized by the solid state method. The phase was found to be characterized by monoclinic symmetry (sp. gr. P2/c) with the following unit cell parameters: a = 7.942(1) Å, b = 5.868(5) Å, c = 18.201(6) Å, b = 91.52(9). Comprehensive investigations of electrical properties were carried out; ceramic material based on the complex oxide was shown to be a predominantly ionic conductor in the temperature range 450–900 oC. The conductivity is due to oxygen-ion transfer in dry conditions and oxygen-ion and proton transfer in wet atmosphere. The proton conductivity value is 4.5·10–5 S/cm, and the proton transport number is ~50% at 700 oC in wet air; at lower temperatures, proton transport becomes dominant. Prolonged treatment of the sample in water vapors below 450 oC leads to hydrolysis decomposition.

Layered nickelates, Ln2NiO4+delta, are promising electrode materials for many electrochemical applications, including solid oxide fuel cells and electrolysis cells. Although Ln2NiO4+delta has been extensively modified by various doping strategies to tune its functional properties, the partial substitution of Ln3+ with Ba2+ remains among the least studied routes. At the same time, such substitution is found to be favorable when Ln2NiO4+delta materials are used for protonic ceramic electrochemical cells based on Ba-containing proton-conducting electrolytes (i.e., BaCeO3, BaZrO3, Ba(Ce,Zr)O3). In this work, which is the third part of a systematic study, Pr2-xBaxNiO4+delta materials are used as electrodes for a proton ceramic fuel cell and as oxygen permeable membranes. The oxygen permeation experiments confirm that the compositions with x = 0.2 and 0.3 prevail over x = 0 and 0.1 in terms of their oxygen-ionic conductivity, while the electrochemical cell characterizations confirm the high electrochemical activity of the Pr1.8Ba0.2NiO4+delta electrode in both fuel-cell- and electrolysis-cell modes. Our research thus confirms that a Ba-doping strategy is highly promising for designing new Ln2NiO4+delta-based phases, simultaneously offering good chemical and thermal compatibility with state-of-the-art proton-conducting electrolytes and high electrochemical performance.

La2-xPrxNi1-yCuyO4+δ (x=0.5, 1, 1.5, y=0.4, 0.6, 0.8) were synthesized by a citrate-nitrate method and studied as cathode materials for IT-SOFCs by Electrochemical Impedance Spectroscopy (EIS) in symmetrical cells based on the Ce0.8Sm0.2O2-δ (SDC) and La28-zW4+zO54+1.5z (z = 0.85, LWO) electrolytes. Phase identification and crystal structure analysis by means of X-ray powder diffraction (XRPD) shows that solubility of copper y decreases with the increase in praseodymium content x due to increasing structural distortions. Thermodynamic stability of La2-xPrxNi1-yCuyO4+δ at intermediate temperatures in air tends to decrease with praseodymium doping level x and increases with copper substitution for nickel y. Oxides with x=0.5 and 0.6≤y≤0.8 are shown to be thermodynamically stable at 700 °C in air. Electrochemical performance of the La2-xPrxNi1-yCuyO4+δ electrodes improves with praseodymium and copper doping. The results of EIS measurements at different temperatures and oxygen partial pressures (P(O2)) reveal that the rate-determining step of the overall electrochemical process is charge transfer, which can be a combination of surface diffusion and bulk diffusion. EIS studies in dry and wet air indicate the presence of proton conduction in the studied electrodes. The area-specific resistances (ASRs) for La2-xPrxNi1-yCuyO4+δ with x=0.5, y=0.6 and y=0.8 in contact with SDC are comparable with those reported for Pr2NiO4+δ and equal to 0.07 and 0.065 Ω cm2 at 800 °C.

A CO2-stable, 2-stable, easily sintered proton-conducting oxide electrolytes based on solid solution Ba 7 In 6 Al 2- x Zn x O 19-0.5 x with hexagonal structure has been synthesized for the first time. Within the homogeneity region (0 <= x <= 0.10), there is an increase in unit cell parameters, cell volumes and free cell volumes. The addition of Zn2+ 2+ markedly improved the sinterability of the material. The relative density of the ceramics of the doped samples reached 95 % at lower sintering temperatures than the parent phase. The electrical conductivity was studied using electrochemical impedance spectroscopy. Upon doping the oxygen-ion conductivity increased by 0.25 orders of magnitude at 800 degrees C. Proton transport was predominant below 500 degrees C for a wet atmosphere (pH2O 2 O = 1.92 center dot 10-2 atm). The investigated phases Ba 7 In 6 Al 2- x Zn x O 19-0.5 x are capable of hydration and incorporate up to 1.45 mol H2O 2 O vs 0.41 mol H2O 2 O for the parent phase. The studied phases exhibit chemical resistance to CO2 2 under heat treatment at 600 degrees C. It was shown that solid solution Ba 7 In 6 Al 2- x Zn x O 19-0.5 x is a promising electrolyte material for intermediate-temperature fuel cells.

La 1.4 Ca 0.6 Ni 0.6 Fe 0.4 O 4+ delta (LCNF), La 1.4 Sr 0.6 Ni 0.6 Fe 0.4 O 4+ delta (LSNF), La 1.4 Ba 0.6 Ni 0.6 Fe 0.4 O 4+ delta (LBNF) have been synthesized by the citrate -nitrate technique. The X -Ray powder diffraction (XRPD) results show an increase in the unit cell parameters and the unit cell volume with the increase in radius of the alkaline earth metal. The oxides possess oxygen excess equal to 0.06 at room temperature and demonstrate semiconductor -type behavior in the 25 - 950 degrees C range. The thermal expansion coefficient (TEC) determined in the 200 - 1000 degrees C interval decreases from 13.9 x 10 -6 (A=Ca) to 13.2 x 10 -6 & Kcy; - 1 (A=Ba) with increasing the dopant size. The electrochemical studies have revealed that the overall polarization resistance of La 1.4 A 0.6 Ni 0.6 Fe 0.4 O 4+ delta is equal to 1.85, 2.61 and 0.4 Omega cm 2 at 800 degrees C for A=Ca, Sr and Ba, respectively. The predominant contribution to the polarization resistance is assigned to the charge transfer - ionic diffusion in the electrodes. It decreases in the row LSNF-LCNFLBNF, which correlates with the increase in ionic conductivity in the oxides.

The magnetic properties of disordered Nd0.5Ba0.5Mn0.5Fe0.5O3-delta/2 and ordered NdBaMnFeO6-delta perovskites were investigated through temperature- and field-dependent DC-magnetization measurements. The temperature dependence of magnetic susceptibilities revealed that antiferromagnetic ordering occurs at temperatures below 185 K for the disordered Nd0.5Ba0.5Mn0.5Fe0.5O3-delta/2 sample, whereas the ordered NdBaMnFeO6-delta perovskite exhibited a paramagnetic state throughout the entire temperature range examined. Notably, the disordered sample exhibited a glassy state, even at room temperature, which transformed into an antiferromagnetic state under higher applied magnetic fields. The magnetic ordering in the disordered Nd0.5Ba0.5Mn0.5Fe0.5O3-delta/2 perovskite and the magnetic-disordering state in the structurally ordered NdBaMnFeO6-delta perovskite could be attributed to the alteration of the oxidation state of Mn.

Surface oxygen exchange in the La2NiO4+a and La1.5Sr0.5Ni1-yFeyO4+a (y = 0.3, 0.4) oxides is analyzed using the data on oxygen permeability through the membranes with different thicknesses measured under various oxygen partial pressure P(O2) gradients in the 800 -1000 & DEG;C range. The increase in P(O2) gradient induced surface limitations in La2NiO4+a leading to a predominant role of surface exchange in the overall oxygen flux. The origin of surface exchange limitations in La2NiO4+a is ascribed to a relatively fast decrease in oxygen excess and Ni3+ concentration with P(O2) reduction compared to La1.5Sr0.5Ni0.7Fe0.3O4+a and La1.5Sr0.5Ni0.6Fe0.4O4+a, which retained an oxygen excess. Faster surface exchange kinetics for La1.5Sr0.5Ni0.6Fe0.4O4+a in comparison with that for La1.5Sr0.5Ni0.7Fe0.3O4+a is interpreted on the basis of surface microstructure obtained by electron backscatter diffraction (EBSD). It is suggested that the observed changes in size, shape and crystallographic orientation of grains in La1.5Sr0.5Ni0.6Fe0.4O4+a (compared to La1.5Sr0.5Ni0.7Fe0.3O4+a) could result in a higher amount of 3d-metal cations in surface layers of the oxide. & COPY; 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

A complex oxide Ba 5 In 1.9 Y 0.1 Al 2 ZrO 13 with hexagonal perovskite structure ( a = 5.971(4) Å, с = 24.012(1) Å) is prepared for the first time. The phase is found to dissociative-absorb water from gas phase, the degree of hydration being as high as 0.39 mol Н 2 О. It was found by using IR-spectroscopy that protons are present therein as energetically nonequivalent ОН – -groups involved in hydrogen bonds of diverse strength. Isovalent yttrium-doping of the Ba 5 In 2 Al 2 ZrO 13 phase is shown not to lead to any valuable change in the oxygen-ion-conductivity as compared with the Ba 5 In 2.1 Al 2 Zr 0.9 O 12.95 acceptor doping that allows increasing the oxygen-ion-conductivity by a factor of 1.3. Both types of doping lead to increase in the proton conductivity and, as a corollary to this, an increase in the proton concentration. For these phases the degree of hydration depends on the cell parameters, hence, is determined by space availability for ОН – -groups in the barium coordination. Proton transport dominates in the Ba 5 In 2 Al 2 ZrO 13 , Ba 5 In 2.1 Al 2 Zr 0.9 O 12.95 , and Ba 5 In 1.9 Y 0.1 Al 2 ZrO 13 phases below 600 о С in humid atmosphere ( p H 2 О = 1.92 × 10 –2 atm).

A complex oxide Ba5In1.9Y0.1Al2ZrO13 with hexagonal perovskite structure (a = 5.971(4) Å, с = 24.012(1) Å) is prepared for the first time. The phase is found to dissociative-absorb water from gas phase, the degree of hydration being as high as 0.39 mol Н2О. It was found by using IR-spectroscopy that protons are present therein as energetically nonequivalent ОН–-groups involved in hydrogen bonds of diverse strength. Isovalent yttrium-doping of the Ba5In2Al2ZrO13 phase is shown not to lead to any valuable change in the oxygen-ion-conductivity as compared with the Ba5In2.1Al2Zr0.9O12.95 acceptor doping that allows increasing the oxygen-ion-conductivity by a factor of 1.3. Both types of doping lead to increase in the proton conductivity and, as a corollary to this, an increase in the proton concentration. For these phases the degree of hydration depends on the cell parameters, hence, is determined by space availability for ОН–-groups in the barium coordination. Proton transport dominates in the Ba5In2Al2ZrO13, Ba5In2.1Al2Zr0.9O12.95, and Ba5In1.9Y0.1Al2ZrO13 phases below 600оС in humid atmosphere (pH2О = 1.92 × 10–2 atm).

The conductivity in the monoclinic polymorphs of Ln(2)MoO(6) (Ln = Sm, Gd, Dy) oxymolybdates was investigated by theoretical and experimental methods. A theoretical approach consisted of geometrical-topological analysis, bond valence site energy, kinetic Monte-Carlo (KMC) modeling and density functional theory (DFT) calculations. The theoretical results have shown that oxygen ionic conductivity is possible in all oxymolybdates with DFT migration energy <1.39 eV. We also calculated oxygen ionic conductivity at various temperatures (500-800 degrees C) using KMC modeling and found values higher than 10(-3.5) S/cm at 800 degrees C, which was in agreement with the experimental measurements. The total conductivity achieved similar to 10(-5) S/cm for Sm2MoO6, similar to 10(-4) S/cm for Gd2MoO6 and similar to 10(-3) S/cm for Dy2MoO6 at 800 degrees C according to impedance spectroscopy data. The oxygen pressure isotherms in the Ln(2)MoO(6) (Ln = Sm, Gd, Dy) indicated electronic conductivity contribution in the temperature range of 500-800 degrees C. The experimental electromotive force (EMF) method also showed an increase in the contribution of electronic conductivity with the temperature growth. The activation energy of oxygen ionic diffusion according to EMF data was in the range of 0.78-1.27 eV.

Tetragonal perovskite phase Ce0.9Ca0.1AlO2.95 + x was obtained for the first time. Such phase, containing cerium in the oxidation state of 3+, can be promising anode materials for a solid oxide fuel cells (SOFCs). Ce0.9Ca0.1AlO2.95 + _ (space group I4/mcm) was synthesized by the solid-phase method at 1400 & DEG;C in a nitrogen flow with using ammonium oxalate (NH4)2C2O4 to create a reducing atmosphere. Thermogravimetry results showed that Ce0.9Ca0.1AlO2.95 + x was stable to oxidation up to 500 & DEG;C in air and up to 700 & DEG;C in argon (partial pressure of oxygen pO2 =10-4 bar). The thermal expansion coefficient measured by dilatometry was equal to 11.16.10-6 K-1. The temperature dependences of the electrical conductivity (for undoped phase CeAlO3 s = 1.10-3 S/cm and for doped Ce0.9Ca0.1AlO2.95 + x s = 3.10-2 S/cm at 500 & DEG;C in air) were obtained by the electrochemical impedance spectroscopy measurements). The electrical conductivity of these samples at the temperatures range of 350-500 & DEG;C was almost independent of the partial pressure of oxygen pO2 from 10-18 to 0.21 bar, however, there was a slight negative slope at T > 500 & DEG;C (pO2). The total ionic transport numbers measured by the EMF method were close to 1.10-3, which indicated the dominance of electronic conductivity. The measurement of the sign of the thermal-EMF showed that positive charge carriers (holes) were dominant charge carriers.& COPY; 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

The Ruddlesden‒Popper phases pertain to numerous promising materials with the mixed ionic-electronic conductivity used in devices such as oxygen-conducting membranes, solid oxide fuel cells (SOFC), and electrolyzers, which operate in the intermediate temperature region. Their high total conductivity and oxygen mobility make these materials candidates for the mentioned applications. The structure, the oxygen mobility, and the electrochemical characteristics of the promising materials La 1.7 Ca 0.3 Ni 1 – x Cu x O 4 + δ ( x = 0–0.4) are studied. According to the high-precision XRD data, all synthesized materials are single-phased and have the tetragonal structure. The unit cell parameter c and the cell volume increase upon doping with copper. The content of overstoichiometric interstitial oxygen decreases with doping and the compositions with the high copper content become oxygen deficient. The samples are characterized by the nonuniform oxygen mobility. By and large, the trend for the decrease in the oxygen mobility with the increase in the Cu content is observed in the series of La 1.7 Ca 0.3 Ni 1 – x Cu x O 4 + δ samples. By impedance spectroscopy studies, it is shown that the electrodes with the La 1.7 Ca 0.3 Ni 1 – x Cu x O 4 + δ functional layers with the copper content x > 0.2 have a higher electrochemical activity. The factors responsible for the efficiency of electrodes are analyzed. The results obtained in this study demonstrate that La 1.7 Ca 0.3 Ni 0.6 Cu 0.4 O 4 + δ materials are the candidates for the air electrodes in electrochemical devices.

The La1.7Ca0.3Ni1−yCuyO4+δ (y = 0.0–0.4) nickelates, synthesized via a solid-state reaction method, are investigated as prospective materials for oxygen permeation membranes and IT-SOFC cathodes. The obtained oxides are single-phase and possess a tetragonal structure (I4/mmm sp. gr.). The unit cell parameter c and the cell volume increase with Cu-substitution. The interstitial oxygen content and total conductivity decrease with Cu-substitution. The low concentration of mobile interstitial oxygen ions results in a limited oxygen permeability of Cu-substituted La1.7Ca0.3NiO4+δ ceramic membranes. However, increasing the Cu content over y = 0.2 induces two beneficial effects: enhancement of the electrochemical activity of the La1.7Ca0.3Ni1−yCuyO4+δ (y = 0.0; 0.2; 0.4) electrodes and decreasing the sintering temperature from 1200 °C to 900 °C. Enhanced electrode activity is due to better sintering properties of the developed materials ensuring excellent adhesion and facilitating the charge transfer at the electrode/electrolyte interface and, probably, faster oxygen exchange in Cu-rich materials. The polarization resistance of the La1.7Ca0.3Ni1.6Cu0.4O4+δ electrode on the Ce0.8Sm0.2O1.9 electrolyte is as low as 0.15 Ω cm2 and 1.95 Ω cm2 at 850 °C and 700 °C in air, respectively. The results of the present work demonstrate that the developed La1.7Ca0.3Ni0.6Cu0.4O4+δ-based electrode can be considered as a potential cathode for intermediate-temperature solid oxide fuel cells.

La2NiO4+delta, La1.4Ca0.6Ni0.6Fe0.4O4+delta (LCNF0604), La1.4Sr0.6Ni0.6Fe0.4O4+delta (LSNF0604), La1.4Sr0.6Ni0.5Fe0.5O4+delta(LSNF0605) and La1.5Sr0.5Ni0.6Fe0.4O4+delta (LSNF0504) were synthesized by the citrate-nitrate technique with the following four annealing steps at 950 degrees C in air (La2NiO4+delta, LCNF0604, LSNF0604) or in atmosphere with the reduced (10(-5) atm) oxygen partial pressure (LSNF0605, LSNF0504). Phase purity of the samples is confirmed by the X-ray powder diffraction (XRPD). Electrochemical impedance spectroscopy studies of the symmetrical cells based on the proton-conducting La28-zW4+zO54+1.5z (z = 0.85, LWO85) electrolyte reveal that the polarization resistance (R-p) decreases in the row LCNF0604>La2NiO4+delta>LSNF0504>LSNF0604>LSNF0605 in the temperature interval of 600-800 degrees C in wet air. The process at low frequencies related to the surface exchange, provides the most significant contribution to the polarization resistance of the studied cells. Higher polarization resistance for the La2NiO4+delta/LWO85 cell can be associated with blocking of protons/protonic species. The minimal Rp value of 1 Omega cm(2) at 800 degrees C in wet air is demonstrated by the LSNF0605/LWO85 symmetrical cell. The maximal power density for the anode-supported LSNF0605/LWO85/Ni-LWO85 single fuel cell is equal to 55 mW cm(-2) at 750 degrees C. The performance of the fuel cell is limited by the formation of La2O3 at the LWO85/Ni-LWO85 interface due to chemical interaction between NiO and LWO85. To improve the performance of the studied fuel cell the development of new proton-conducting buffer layer stable to LWO85 is required.

La2NiO4+δ, La1.4Ca0.6Ni0.6Fe0.4O4+δ (LCNF0604), La1.4Sr0.6Ni0.6Fe0.4O4+δ (LSNF0604), La1.4Sr0.6Ni0.5Fe0.5O4+δ (LSNF0605) and La1.5Sr0.5Ni0.6Fe0.4O4+δ (LSNF0504) were synthesized by the citrate-nitrate technique with the following four annealing steps at 950 °C in air (La2NiO4+δ, LCNF0604, LSNF0604) or in atmosphere with the reduced (10−5 atm) oxygen partial pressure (LSNF0605, LSNF0504). Phase purity of the samples is confirmed by the X-ray powder diffraction (XRPD). Electrochemical impedance spectroscopy studies of the symmetrical cells based on the proton-conducting La28−zW4+zO54+1.5z (z = 0.85, LWO85) electrolyte reveal that the polarization resistance (Rp) decreases in the row LCNF0604>La2NiO4+δ>LSNF0504>LSNF0604>LSNF0605 in the temperature interval of 600–800 °C in wet air. The process at low frequencies related to the surface exchange, provides the most significant contribution to the polarization resistance of the studied cells. Higher polarization resistance for the La2NiO4+δ/LWO85 cell can be associated with blocking of protons/protonic species. The minimal Rp value of 1 Ω cm2 at 800 °C in wet air is demonstrated by the LSNF0605/LWO85 symmetrical cell. The maximal power density for the anode-supported LSNF0605/LWO85/Ni-LWO85 single fuel cell is equal to 55 mW cm−2 at 750 °C. The performance of the fuel cell is limited by the formation of La2O3 at the LWO85/Ni-LWO85 interface due to chemical interaction between NiO and LWO85. To improve the performance of the studied fuel cell the development of new proton-conducting buffer layer stable to LWO85 is required.