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The first example of a photocatalyst-free strategy for the photo-promoted synthesis of gem-dihaloenones is developed.

Based on Eshelby’s equivalent inclusion theory, the four-phase model and the interaction direct derivative estimate, the prediction model of effective thermal expansion coefficient of composite containing multiple types of inclusion in anisotropic matrix was established. The effective thermal expansion coefficient of eutectic composite containing defects was calculated. And then the influence of defects and inclusions on the effective thermal expansion coefficient is discussed in detail. The results show that the influence of inclusions will be amplified by defects when there are multiple inclusions in the matrix. Therefore, the interaction direct derivative estimate cannot accurately predict the influence of defect distribution on thermal expansion coefficient of eutectic composite ceramics.

A PBC–GDC composite with coherent interface structure shows remarkable ORR activity and low polarization resistance under IT-SOFC service conditions.

Symmetrical solid oxide fuel cells (SSOFCs), in which the same material serves as anode and cathode simultaneously, have attracted substantial attention because of the simplified electrode/electrolyte interface issue and cell fabrication process. The exploration of suitable electrode material for SSOFC is a great challenge. In this work, Mg-doped SmBaMn1.9Mg0.1O5+δ (SBMM) with Sm-Ba layered ordering is proposed as SSOFC electrode material. The SBMM shows high structure reversibility upon thermal and redox cycling, with orthorhombic Pmmm symmetry in air and tetragonal P4/nmm structure in reducing atmosphere. It exhibits similar thermal expansion coefficients of 15.14(1) × 10−6 K-1, 14.72(6) × 10−6 K-1 in 5% H2/Ar and air, respectively. Mg-doping decreases the chemical-induced expansion of SBMM remarkably, which ensures good thermomechanical compatibility of SBMM with La0.8Sr0.2Ga0.8Mg0.2O3-δ (LSGM) electrolyte and thus leads to a lower polarization resistance. The LSGM electrolyte (300 μm) supported symmetrical cell with SBMM electrodes delivers a maximum power density of 596 mW cm-2 at 900 °C. These results demonstrate that SmBaMn1.9Mg0.1O5+δ is a highly promising electrode material for SSOFCs.

Polyanion-type Na3V2(PO4)3 (NVP) is an overwhelmingly attractive cathode material for sodium-ion batteries (SIBs) because of its high structural stability and fast Na+ mobility. However, its practi...

Exsolution of catalytic nanoparticles (NPs) from perovskites has arisen as a flexible method to develop high-performance functional materials with enhanced durability for energy conversion and catalytic synthesis applications. Here, we unravel the interface structure of the in situ exsolved alloy nanoparticles from the double perovskite substrate on the atomic scale. The results show that the Co-Fe alloy NPs exsolved topologically from the {100} facets terminations of the Sr2FeMo0.65Co0.35O6-δ (SFMC) double perovskite along ⟨100⟩ directions exhibiting the same orientation and identical crystal structure. The lattice planes of these two phases align and insert into each other at the interface, forming a smooth and continuous coherent connection. The presence of moire patterns at the interface confirms the topological exsolution mechanism. The coherent interface can significantly reduce the interfacial energy and therefore stabilize the exsolved nanoparticles. Therefore, excellent and stable electrochemical performance of the NP-decorated SFMC perovskite is observed as the anode for solid oxide fuel cells. Our contribution promotes a fundamental understanding of the interface structure of the in situ exsolved alloy nanoparticles from perovskite substrate.

Series of Nd2-xNi1-yCuyO4±δ Ruddlesden-Popper-type oxides is obtained by auto-combustion synthesis method and systematically characterized concerning phase composition, formation of solid state solution, crystal structure, oxygen content, as well as regarding transport properties and oxygen permeability when applied as mixed conducting ceramic membranes. The A-site deficiency x is discussed in terms of structural stability and its effect on the oxygen content, with ongoing modification of total electrical conductivity observed. In selected Nd2-xNi0.75Cu0.25O4±δ oxides the dominating oxygen defects at high temperatures can be changed from oxygen interstitials to vacancies by the induced A-site deficiency, which affects bulk- and surface-related transport coefficients, as it is observed in electrical conductivity relaxation studies. The optimized Nd1.9Ni0.75Cu0.25O4±δ sinters having increased ionic conductivity, as well as fine, well-sintered microstructure allow to achieve one of the higher reported oxygen fluxes for CO2-stable Ruddlesden-Popper-based ceramic membranes (e.g. 0.49 mL cm−2 min−1 at ca. 880 °C for 1.05 mm thickness).

Modified by Sm0.2Ce0.8O2−δ (SDC) nanoparticles (NPs), SmBaCo2O5+δ (SBCO) double perovskite oxide is evaluated as a promising cathode material for intermediate temperature solid oxide fuel cells. The SDC NPs are epitaxially grown on the surface of SBCO with (220) planes of SDC aligning smoothly to (020) or (100) planes of SBCO, forming a tight, coherent connection at the interface. The influence of this modification on thermal expansion, oxygen diffusion, electrical conductivity and electrochemical properties is investigated thoroughly in this work. The designed SBCO–SDC cathode material demonstrates a lower thermal expansion coefficient (TEC), ∼16.4 × 10−6 K−1, than that of the unmodified SBCO, ∼20.9 × 10−6 K−1. While SDC coating results in a decreased total electrical conductivity, it facilitates oxygen bulk diffusion and improves the surface exchange reaction kinetics. Coating with SDC NPs can accelerate the rate-determining process of dissociation of the absorbed molecular oxygen, especially at intermediate temperatures. Accordingly, the constructed symmetrical cell with the La0.8Sr0.2Ga0.8Mg0.2O3−δ (LSGM) electrolyte shows lower polarization resistance values, if the SBCO–SDC cathode is utilized. Also, the LSGM electrolyte-supported (300 μm) full cell is found to deliver a high power density of 800 mW cm−2 at 800 °C. Owing to the strong and coherent interfacial connection, the developed cathode demonstrates a relatively steady electrochemical performance.

SmBaCo0.5Mn1.5O5+δ oxide with Sm-Ba cation-ordered perovskite-type structure is synthesized and examined in relation to whole RBaCo0.5Mn1.5O5+δ series (R: selected rare earth elements). Presence of Sm and 3:1 ratio of Mn to Co allows to balance physicochemical properties of the composition, with moderate thermal expansion coefficient value of 18.70(1)·10−6 K−1 in 300–900 °C range, high concentration of disordered oxygen vacancies in 600–900 °C range (δ = 0.16 at 900 °C), and good transport properties with electrical conductivity reaching 33 S cm−1 at 900 °C in air. Consequently, the compound enables to manufacture catalytically-active cathode, with good electrochemical performance measured for the electrolyte-supported laboratory-scale solid oxide fuel cell with Ni-Gd1.9Ce0.1O2-δ|La0.4Ce0.6O2-δ|La0.8Sr0.2Ga0.8Mg0.2O3-δ|SmBaCo0.5Mn1.5O5+δ configuration, for which 1060 mW cm−2 power density is observed at 900 °C. Furthermore, the tested symmetrical SmBaCo0.5Mn1.5O5+δ|La0.8Sr0.2Ga0.8Mg0.2O3-δ|SmBaCo0.5Mn1.5O5+δ cell delivers 377 mW cm−2 power density at 850 °C, which is a promising result.

Safety issues affecting traditional lithium-ion batteries with liquid electrolyte can be successfully overcome by application of a solid electrolyte. Among various candidate materials, perovskite-type compounds, typically from Li3xLa2/3−xTiO3 group, are known to exhibit superior Li+ ionic conductivity. However, the ever-increasing requirement for high ionic conductivity necessitates the improvement of its structure and composition. In this work, Sr2+ cations, having ionic radius larger than La3+, are doped at the La-site in order to enlarge the unit lattice parameter and so facilitate the lithium ion migration process. At the same time, Sr doping can increase the lithium ion concentration of Li0.33+xLa0.56−xSrxTiO3 oxides as charge compensation. Both of them favor the increase of lithium ion conductivity. The Sr substitution induces structure transformation from tetragonal to cubic structure. The prepared dense Li0.36La0.53Sr0.03TiO3 (x = 0.03) ceramic electrolyte exhibits a high ionic conductivity of 1.95 × 10−3 S cm−1 at 303 K, which is about twice as high as that of the pristine material.

The design of a symmetrical solid oxide fuel cell comprising identical anode and cathode material brings numerous advantages over a conventional cell with different anode and cathode materials. In this report, A-site layered perovskite with an SmBaMn2O5+δ composition is synthesized and thoroughly investigated as the electrode material for symmetrical cells. The SmBaMn2O5+δ material with a P4/nmm structure remains stable in both reducing and oxidizing atmospheres at elevated temperatures, but with a difference of ca. 1 mol in the oxygen content per mole of SmBaMn2O5+δ between the oxidized and the reduced materials. The SmBaMn2O5+δ material shows high electrical conductivity in air and an acceptable value in 5% H2/Ar at 750–900 °C, and it exhibits outstanding catalytic activity toward oxygen reduction and hydrogen oxidization reactions with polarization resistance values of 0.066 and 0.313 Ω cm2 in air and humidified H2 at 900 °C, respectively. The power density of a laboratory-scale La0.8Sr0.2Ga0.8Mg0.2O3−...

A series of La0.15Sr0.85FeO3-δ-xLa0.15Ce0.85O2-δ (LSFO-xLDC) and Cu-doped LSFO-70La0.15Ce0.8Cu0.05O2-δ (LSFO-70LDCC) dual-phase membranes were prepared by one-pot method and evaluated systematically as high CO2-tolerant oxygen separation membranes. The results reveal that the stability of the membranes is improved by compositing LDC. Among the studied compositions, the LSFO-70LDC compound shows excellent stability under reducing atmosphere and CO2-containing atmosphere. The oxygen permeability of LSFO-70LDC membrane with 0.6 mm thickness is 0.49 mL cm−2 min−1 at 950 °C. In addition, LSFO-70LDC shows outstanding long-term stability with stable oxygen permeability of 0.30 mL cm−2 min−1 at 900 °C for 100 h. Cu-substitution prominently enhances the oxygen permeation performance of the LSFO-70LDCC dual-phase membrane, which delivers an enhanced oxygen permeability of 0.65 mL cm−2 min−1 at 950 °C. Moreover, the LSFO-70LDCC membrane exhibits excellent long-term stability for 100 h at 900 °C in both pure He and CO2. These results indicate that the developed LSFO-70LDC and LSFO-70LDCC dual-phase membranes are very promising membranes for oxygen separation.

La9.67Si6-xCuxO26.5-x (LSC, x = 0, 0.1, 0.3 and 0.5) are synthesized by a citric-nitrate method. Substitution Si with Cu promotes the densification process of silicate apatite. Unit cell parameters and volume increase linearly with Cu content. The Rietveld refinement reveals a much more distorted (Si,Cu)O4 tetrahedra in the oxygen stoichiometric La9.67Si5.5Cu0.5O26 sample. The structural observation from high temperature XRD implies a second-order phase transition in La9.67Si5.5Cu0.5O26. Cu-doping decreases the activation energy of oxygen ion conduction and increases the conductivity of LSC materials in the temperature range of 550–800 °C. La9.67Si5.5Cu0.5O26 shows the conductivity values of 29.3 and 12.3 mS cm−1 at 800 °C and 650 °C, respectively. The oxygen ion transference number of La9.67Si5.5Cu0.5O26 is higher than 0.99. These attractive properties make the La9.67Si5.5Cu0.5O26 a promising oxygen ion conducting electrolyte for applications of solid oxide fuel cells, oxygen sensors, oxygen separation membranes, etc.

Na3V2(PO4)3 with a 3D open NASICON framework can accommodate a wide range of Na contents, which makes it capable of working as both a cathode and anode material. However, severe capacity degradation and inferior rate capability resulting from low electronic/ionic conductivities and poor structural stability have hindered its practical implementation. Herein, excellent sodium storage performance of Na3V2(PO4)3 is realized by delicate lattice modulation. Aliovalent Ca2+ substitution for V3+ increases both the electronic and ionic conductivities by producing electronic defects and enlarging the sodium ion migration channels. DFT calculations reveal that the fifth Na ion intercalation/deintercalation produces a large lattice volume change, which is possibly the origin of the poor redox reaction reversibility of Na3V2(PO4)3 at low potential (∼0.3 V vs. Na+/Na). The Ca2+ doping enhances significantly the structural stability to suppress the large crystal lattice distortion during the anode reaction process. The multiple effects enable superior rate-capability and ultralong cycle-life of Ca-doped Na3V2(PO4)3 as both a cathode and anode material. The symmetric full cell constructed with the optimized Na3V1.95Ca0.05(PO4)3@C electrode delivers a very high energy density of 166 W h kg−1 and an exceptional cycling stability (0.02% capacity decay per cycle over 2000 cycles at 10C rate). This study provides a feasible strategy for obtaining high-rate and long cycle-life electrode materials for high-efficiency energy storage.

It is shown that appropriately doped Cu-based perovskite-type oxides exhibit high catalytic activity toward the oxygen reduction reaction at high temperatures, surprisingly making them suitable candidates for the preparation of air electrodes for solid oxide fuel cells. The proposed substitution in the La-sublattice of LaCuO3−δ by Ba and/or Sr (i.e. La4BaCu5O13±δ, La3SrCu4O10±δ and La3Sr0.6Ba0.4Cu4O10±δ compositions) allows stabilization of the perovskite-type structure at ambient pressures in a wide range of temperatures. The materials exhibit extraordinarily high total electrical conductivity associated with the presence of mixed Cu3+/Cu2+ states, limited thermal expansion due to suppressed oxygen release at high temperatures, as well as suitable thermal and chemical stability. Moreover, as derived from first principles calculations for the La4BaCu5O13±δ-based supercell, the activation energy of migration of the oxygen vacancies for La4BaCu5O13−δ is low, ca. 0.4 eV. In contrast to Co, copper is cheap, environmentally benign and thermal treatment of its oxides does not require high temperatures, and therefore, the proposed Cu-based compounds are attractive for preparation of the electrode layers. For the selected La4BaCu5O13±δ oxide the influence of sintering temperature on the cathodic polarization resistance is presented, with the lowest recorded value of 0.03 Ω cm2 at 900 °C. The performance of a button-type solid oxide fuel cell with the optimized La4BaCu5O13±δ-based air electrode screen-printed on the La0.2Ce0.8O2−δ buffer layer and La0.8Sr0.2Ga0.8Mg0.2O3−δ solid electrolyte is good, with the highest power output exceeding 1 W cm−2 at 900 °C for the cell fuelled with wet H2.

Belonging to the not fully explored REBaCo2-xMnxO5+δ system, a series of REBaCoMnO5+δ (RE: selected rare earth elements) oxides having perovskite-type structure is synthesized and studied in terms ...

We report here a mixed oxygen ionic-electronic conductor-molten carbonate composite membrane for high temperature CO2 separation. Mo-doping at Fe-site of La0.2Sr0.8FeO3-δ (LSF) is attempted to address its stability issue in CO2 or carbonate-containing environment. The La0.2Sr0.8Fe0.9Mo0.1O3-δ (LSFM)-molten carbonate membrane with 1 mm thickness delivers a CO2 permeation flux of 1.57 × 10−3 mol m−2 s−1 at 800 °C with 50% CO2 + 50 % N2 (total 1 atm) as feeding gas and pure He (1 atm) as sweeping gas, compared to 0.737 × 10−3 mol m−2 s−1 for the LSF counterpart. The CO2 permeation flux further increases to 2.25 × 10−3 mol m−2 s−1 for membrane prepared with Al2O3 coated LSFM substrate. An even higher CO2 permeability of 2.69 × 10−3 mol m−2 s−1 is demonstrated for LSFM-molten carbonate membrane at 800 °C when using simulated flue gas (15% CO2 + 10% O2 + 75 % N2 in total 1 atm) as feeding gas. The membrane also exhibits relatively stable CO2 and O2 fluxes during 50 h test at 750 °C. The designed LSFM-molten carbonate membrane can be potentially used as a reactor for dry methane reforming and partial oxidation of methane with flue gas as direct feedstock.

Correction for ‘Enhanced oxygen reduction kinetics of IT-SOFC cathode with PrBaCo2O5+δ/Gd0.1Ce1.9O2−δ coherent interface’ by Yang Zhang et al., J. Mater. Chem. A, 2022, 10, 3495–3505, DOI: 10.1039/D1TA09615J.

Eutectic composite ceramics has a wide range of applications in the aerospace industry due to its excellent mechanical properties. The rupture stress of the materials is a subject of considerable importance. Eutectic composite ceramics primarily consist of rod-shaped crystals, with a small amount of particles and preexisting defects dispersed throughout. Aligned nano-micron fibers are embedded within the rod-shaped crystals. Rupture stress of a eutectic composite ceramic depends on its fracture surface energy and preexisting defects. In this study, the equivalent fracture surface energy of a eutectic ceramic composite was calculated based on its additional fracture work. Next, the effects of the preexisting defects were considered. Then, a micromechanical model of the eutectic composite ceramic was established based on its microstructural characteristics. The defects were assumed to be lamellar, and the surrounding matrix was assumed to be transversely isotropic. Using this information, the rupture stress of the eutectic ceramic composite was predicted. A comparison of the theoretical and experimental results indicated that the predicted rupture stresses corresponded with the tested data.

Based on the microscopic characteristics of fiber reinforced composite ceramics, the slippage stress at the interface of composite ceramics under external loading is analyzed. The relation between the applied strain of the triangular symmetrical eutectic and the load of composite ceramics is confirmed. And the maximum shear stress that the triangular symmetrical eutectic can endure is computed. The yield shear stress was calculated by the hardness and fracture toughness of composite ceramics. When the maximum shear stress which the triangular symmetrical eutectic can bear is equal to the yield shear stress, the slipping stress of micro-mechanical interface in composite ceramics is obtained. The results showed that fiber inclusions in the eutectic having smaller dimension and larger volume content would provide larger partial plastic deformation of composite ceramics.

Study of damage and fracture models to analyze the fracture mechanism of eutectic composite ceramics is of considerable importance because no accurate fracture models are available for these materials. Eutectic composite ceramics are composed of microcells with random direction. We present herein a model that predicts the damage and fracture of eutectic composite ceramics based on analysis of defect stability and the damage localization band. Firstly, given the microstructure of eutectic composite ceramics, a mesodomain and a microcell model are constructed. The local stress field in the mesodomain is then analyzed based on the interaction direct derivative estimate. Secondly, the stability of a defect around particles in a microcell is analyzed, and the stress intensity factor of an annular defect under the applied stress field and the residual stress field in the particle are calculated. The stress intensity factor of a defect is controlled by the residual stress when the defect extension is small. However, it is controlled by the applied stress when the defect extension is large. Finally, a model for the damage localization band at the crack tip is constructed based on the Dugdale–Barenblatt model. The residual intensity is the important factor affecting the length of the damage localization band. When the damage variables reach their largest value, the residual intensity and the length of the damage localization band attain their minimum value. This work provides the theoretical basis for further study of the damage mechanics of eutectic composite ceramics and guides the engineering applications of these materials.

Na3V2(PO4)3 has shown great promise in next-generation cathode materials for sodium-ion batteries owning to its fast Na+ diffusion in the three-dimensional open NASICON framework and high theoretic...

A mechanical model for the strength prediction of composite ceramics (CC) with nano-interface and micro-interface is presented based on nano-interface damage mechanism and micro-interface damage me...

First principles calculations are employed to understand the effects of Al substitution on the electronic structure, ion dynamics properties, as well as structural stability of Na3V2-xAlx (PO4)3 cathode material. The results reveal that Al doping decreases the band gap energy and transforms the material from indirect to direct band gap electronic structure. Several Na-ion diffusion routes in the crystal structure are proposed and the one with lowest migration energy is identified, which shows one-dimensional transport characteristics along c-axis direction via a curved trajectory. The Al doping increases the Na ion migration energy and thus unfavorable for Na ion diffusion in the crystal. The opposite effects of Al doping on electronic and Na ionic conduction lead to the occurrence of an optimal Al doping level, at which the best electrode reaction kinetics can be expected. The experimental works of the synthesized Na3V2-xAlx (PO4)3 with x = 0–0.4 confirm the theoretical predictions. The sample Na3V1.8Al0.2(PO4)3 with appropriate Al doping exhibits the smallest electrode polarization and superior rate performance. Because of the enhanced binding energy with Al doping as indicated by computation work, the Na3V1.8Al0.2(PO4)3 material displays much stable long-term cycling performance compared to the pristine sample at different temperatures.

In this paper, selected layered cuprates with La2-x(Sr,Ba)xCuO4-δ formula are evaluated as candidate cathode materials for Solid Oxide Fuel Cells. Two synthesis routes, a typical solid state reaction and a sol-gel method yield well-crystallized La1.5Sr0.5CuO4-δ, La1.6Ba0.4CuO4-δ and La1.5Sr0.3Ba0.2CuO4-δ materials having tetragonal I4/mmm space group, but differing in morphology of the powder. Fine powders obtained using sol-gel route seem to be more suitable for preparation of the porous cathode layers having good adhesion on the solid electrolyte, but powders obtained after the solid state route can be also successfully utilized. Investigations of structural and transport properties, the oxygen nonstoichiometry and its change with temperature, thermal expansion, as well as chemical and thermal stability are systematically performed, to evaluate and compare basic physicochemical properties of the oxides. At room temperature the average valence state of copper is found to be in 2.2–2.35 range, indicating oxygen deficiency in all of the compounds, which further increases with temperature. The conducted high-temperature X-ray diffraction tests reveal moderate, but anisotropic thermal expansion of La2-x(Sr,Ba)xCuO4-δ, with higher expansion at temperatures above 400 °C occurring along a-axis, due to the oxygen release. However, the corresponding chemical expansion effect is small and the materials possess moderate thermal expansion in the whole studied temperature range. All compounds show relatively high electrical conductivity at the elevated temperatures, related to the Cu2+/Cu3+ charge transfer, with the highest values recorded for La1.5Sr0.5CuO4-δ. Comprehensive studies of chemical stability of the selected La1.5Sr0.5CuO4-δ material with La0.8Sr0.2Ga0.8Mg0.2O3-δ solid electrolyte revealed complex behavior, with stability being dependent apart from temperature, also on morphology of the powders. A model describing such behavior is presented. While it is possible to minimize reactivity and characterize electrochemical properties of the La1.5Sr0.5CuO4-δ-based cathode layer, usage of the buffer layer is indispensable to maintain full stability. It is shown that mutual chemical compatibility of La1.5Sr0.5CuO4-δ and commonly used La0.4Ce0.6O2-δ buffer layer material is excellent, with no reactivity even at 1000 °C for prolonged time. Laboratory-scale fuel cell with the La1.5Sr0.5CuO4-δ cathode sintered at the optimized temperature is able to deliver 0.16 W cm−2 at 800 °C while fueled with wet hydrogen.

In this work studies on a modification of Cu-based, layered oxides with K2NiF4-type structure are presented concerning formation of cationic nonstoichiometry in the A-sublattice of the parent La2CuO4, as well as an introduction of selected M3 + cations (Sc, Ga, In) at the B-site into La1.9Cu1-xMxO4 and Ni-containing La1.9Cu0.45Ni0.45M0.1O4. It is shown that synthesis of phase-pure La2-xCuO4 can be done with values of x ≤ 0.1, and in the A-site nonstoichiometric materials further doping with M3 + is also achievable. Formation of solid solutions for M3 +-doped samples follows the expected trend, with the widest range observed for the smallest Sc3 + cation, z ≤ 0.1. Apart from a different structural behavior of the doped oxides at high temperatures, it is documented that the discussed substitution affects strongly the oxygen content (e.g. high concentration of the oxygen vacancies is present in La1.9CuO4-δ), as well as electrical conductivity. This is documented by the high-temperature X-ray diffraction, thermogravimetric, iodometic titration and electrical measurements. Since the compounds possess good transport properties, are stable at elevated temperatures, exhibit moderate thermal expansion and are Co-, Sr- and Ba-free, the proposed doping strategy seems interesting concerning development of the oxygen-transporting membranes based on Cu-containing oxides. For example, 1 mm thick La1.9Cu0.9Sc0.1O4-δ membrane was found to deliver 0.37 mL cm− 2 min− 1 oxygen flux at 950 °C, a very high value for the K2NiF4-type materials.

A high CO2-tolerance oxygen permeation membrane BaFe0.95-xCa0.05TixO3-δ (BFCT, x = 0.05–0.15) was designed and prepared. Single cubic perovskite phase can be maintained up to the doping level x = 0.15. The Ti substitution enhances significantly the CO2 tolerance and improve the structural stability under H2 containing atmosphere of BFCT materials. With increasing Ti doping level, the oxygen vacancy concentration decreases and the oxygen ion migration energy increases, leading to a slight decrease in oxygen permeability of BFCT materials. Nevertheless, the sample BaFe0.8Ca0.05Ti0.15O3-δ delivers a high oxygen permeation flux of 1.02 mL min−1 cm−2 at 950 °C for 1 mm thick membrane. The Ti substitution alleviates the lattice oxygen loss and reduces the thermal expansion coefficient of BFCT. A combination study of experimental measurements and first principles calculation was conducted to advance the understanding of Ti effects on the electrical conductivity behavior in BFCT. The BFCT membranes show an excellent long-term operation stability. The high oxygen permeability, good structural stability under CO2 and reducing atmosphere make the BFCT (x = 0.15) a promising membrane for oxygen separation applications.

In this work, a novel series of Mn-containing ReBaCo1.5Mn0.5O5+δ (Re: selected rare earth elements) perovskite-type oxides is studied, with systematic measurements of physicochemical properties being reported. Comparison with the very well-studied, parent ReBaCo2O5+δ allows determination of the role of the introduced manganese concerning modification of the crystal structure at room temperature and its evolution at high temperatures, variation of the oxygen content, thermal stability of the materials, and total electrical conductivity, as well as thermal and chemical expansion. Generally, the presence of Mn cations does not affect the tendency for A-site cation ordering, resulting in an increased unit cell volume of the compounds, as well as causing an increase of the oxygen content. Reduced thermal expansion, together with high values of electrical conductivity and suitable thermal stability, makes the compounds containing larger Re3+ cations attractive from the point of view of application as cathode materials in solid oxide fuel cells. Chemical compatibility studies reveal the sufficient stability of the considered perovskites in relation to Ce0.8Gd0.2O2−δ solid electrolyte, while unexpected, somewhat increased reactivity towards La0.8Sr0.2Ga0.8Mg0.2O3−δ and La0.4Ce0.6O2−δ is also reported. Furthermore, the electrochemical tests of the symmetric cells show strong dependence of the polarization resistance of the electrode on the synthesis and sintering temperatures. For the selected and optimized NdBaCo1.5Mn0.5O5+δ layer employed in the electrolyte-supported (LSGM) symmetric cell with a CGO buffer layer, the cathodic polarization resistance is 0.043 Ω cm2 at 900 °C. A wet hydrogen-fuelled button-type cell with the NdBaCo1.5Mn0.5O5+δ-based cathode is also prepared, delivering the maximum power density exceeding 1.3 W cm−2 at 850 °C.

The effects of A-site substitutions on the interstitial oxygen formation energy and the migration energy in layered A2−xA′xNiO4+δ (A = selected lanthanides, A′ = Ba, Sr, Ca) are investigated by first principles calculations. The interstitial oxygen formation energy is negative, in the range of −4.81 eV to −3.45 eV, strongly supporting easiness of formation of the interstitial oxygen defects in the (A,A′)O rock salt plane. The Pr2NiO4+δ compound shows the lowest formation energy, indicating the highest amount of interstitial oxygen. Doping with alkaline earth cations (A′) increases the formation energy of the interstitial oxygen, which prefers to be located far away from the dopants. Nevertheless, Ca seems to be the best choice, due to relatively low formation energy. Calculations for the four kinds of diffusion paths allow it to be predicted that the oxygen transport in A2−xA′xNiO4+δ is governed by the interstitialcy mechanism in the ab plane, because of the significantly lower energy barriers for this mechanism. An interesting finding is achieved for A2NiO4+δ (A = Pr, Nd, Sm), for which the energy barriers for the interstitialcy transport are negative (−0.47 eV, −0.33 eV and −0.02 eV, respectively), implying that the transition state is more stable than the assumed initial state. A new structural configuration is proposed in this work, with the adjacent apical oxygen located at the adjacent interstitial site, which shows ca. 0.5 eV lower free energy than that of the initial model. This result provides a new understanding for the location of the interstitial and the adjacent apical oxygens from an energetic point of view and supports previously published experimental data. It is found that alkaline earth doping at the A-site deteriorates the interstitial oxygen diffusion in La2−xA′xNiO4.25 materials, but concerning overall transport properties, Ca seems to be a good dopant from an energetic point of view, when compared with Ba and Sr.

Medium-entropy perovskites Sr(FeαTiβCoγMnζ)O3-δ (SFTCM) are investigated as potential cathodes for intermediate temperature solid oxide fuel cell (IT-SOFC). The effects of entropy on crystal structure, thermal expansion coefficients (TEC), electrical conductivity, oxygen surface exchange and bulk diffusion coefficients, electrochemical performance, and long-term stability of SFTCM are systematically investigated. High entropy facilitates the diffusion of oxygen ions but hinders the transmission of electrons. The SFTCM with higher entropy shows a lower TEC, displays suppressed strontium surface segregation, and delivers more stable polarization resistance. Although the catalytic activity towards oxygen reduction reaction was slightly reduced, the maximum power density of the LSGM-supported (250 μm) single cell with SrFe0.25Ti0.25Co0.25Mn0.25O3-δ cathode can still reach 0.85 W cm−2 at 800 °C. All these results suggest that the medium-entropy SFTCM perovskites can be promising cathodes materials for IT-SOFC.

Tin disulfide is considered to be a promising anode material for Li ion batteries because of its high theoretical capacity as well as its natural abundance of sulfur and tin. Practical implementation of tin disulfide is, however, strongly hindered by inferior rate performance and poor cycling stability of unoptimized material. In this work, carbon-encapsulated tin disulfide nanoplates with a (101) plane orientation are prepared via a facile hydrothermal method, using polyethylene glycol as a surfactant to guide the crystal growth orientation, followed by a low-temperature carbon-coating process. Fast lithium ion diffusion channels are abundant and well-exposed on the surface of such obtained tin disulfide nanoplates, while the designed microstructure allows the effective decrease of the Li ion diffusion length in the electrode material. In addition, the outer carbon layer enhances the microscopic electrical conductivity and buffers the volumetric changes of the active particles during cycling. The optimiz...

Rational material design is a key to develop high performance electrode for sodium ion batteries (SIBs). Sandwich-like graphene@MoS2@C sheets (G@MS@C), with MoS2 nanosheets perpendicularly connecting with reduced graphene oxide (rGO) through the direct chemical coupling (C O Mo bonds), are synthesized by a facile two-step method, which involves in situ growth of MoS2 on rGO sheets and a followed amorphous carbon coverage process. The interfacial interaction via the C O Mo bonds can accelerate electron transport rate and enhance structural stability of G@MS@C electrode. Meanwhile, the vertical nanostructure provides more active sites and short diffusion distance for sodium ion reaction, leading to fast electrode reaction kinetics. The rGO sheets and carbon shells not only improve the electrical conductivity of the composite, but also act as buffers to accommodate the volume changes of MoS2 and ensure the integrity of the electrode during cycling. As an anode material for SIBs, the G@MS@C electrode shows superior reversible capacity (520 mAh g−1 after 110 cycles at 100 mA g−1), excellent rate capability (304 mAh g−1 after 200 cycles at 5 A g−1) and stable cycling performance (260 mAh g−1 after 300 cycles at 10 A g−1).

Ca-doping at the Y-site of Y1−xCaxBaCo2O5+δ (YCBC) double perovskites is shown as an effective strategy to develop a highly efficient, stable, lanthanide-free cathode material for intermediate temperature solid oxide fuel cells (IT-SOFCs). The proposed Ca-doping has a beneficial influence on the structural stability, thermal expansion coefficient, electronic and ionic transport, and electrochemical properties of YCBC oxides. The phase stability and durability at evaluated temperature are greatly enhanced by Ca-doping. The thermal expansion coefficients of Y1−xCaxBaCo2O5+δ are calculated to be 18.1–18.7 × 10−6 K−1. At 800 °C, the conductivity is as high as 220 S cm−1 for the Y0.8Ca0.2BaCo2O5+δ sample. Area specific resistances as low as 0.010, 0.018, 0.032, 0.068 and 0.142 Ω cm2 at 850, 800, 750, 700 and 650 °C, respectively, are delivered by the Y0.8Ca0.2BaCo2O5+δ cathode in a La0.8Sr0.2Ga0.8Mg0.2O3−δ electrolyte supported symmetric cell. The maximum power densities of a full cell with the Y0.8Ca0.2BaCo2O5+δ/Ce0.9Gd0.1O2−δ composite cathode are registered to be 1066, 841, 634 and 430 mW cm−2 at 850, 800, 750 and 700 °C, respectively. All the results clearly demonstrate that Ca-doped Y1−xCaxBaCo2O5+δ double perovskites are highly stable and effectively working candidate cathodes for IT-SOFCs.

La 1.5 Sr 0.5 Ni 1- x Fe x O 4+ δ (LSNF, x = 0, 0.3, 0.5) series materials are synthesized as potential cathode materials for intermediate-temperature solid fuel cells by an EDTA-citrate complexation process. The effects of Fe substitution for Ni on the structure, transport property and electrochemical performances are investigated. X-ray diffraction shows that all samples with Fe-doping are identified as single phase materials with a tetragonal I 4/ mmm space group. Fe-doping decreases electrical conductivity of La 1.5 Sr 0.5 Ni 1- x Fe x O 4+ δ . The study of symmetrical cells with La 0.8 Sr 0.2 Ga 0.8 Mg 0.2 O 3- δ (LSGM) as an electrolyte shows a decreasing tendency of polarization resistance ( R p ) of La 1.5 Sr 0.5 Ni 1- x Fe x O 4+ δ with increasing Fe content. The impedance data at different oxygen partial pressures reveal that the electrode reaction is controlled by the molecular oxygen dissociation and charge transfer processes. The substitution of Fe improves the electrode kinetics and enhances the electrochemical performance of LSNF electrode significantly. The LSGM electrolyte (400 μm) supported single cell with La 1.5 Sr 0.5 Ni 0.5 Fe 0.5 O 4+ δ as cathode and Ni-Gd 0.1 Ce 0.9 O 2- δ as anode delivers relatively high power density of 282 mW cm −2 at 800 °C.