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Praseodymium-deficiency Pr0.94BaCo2O6-δ (P0.94BCO) double perovskite has been evaluated as a cathode material for intermediate-temperature solid oxide fuel cells. X-ray diffraction pattern shows the orthorhombic structure with double lattice parameters from the primitive perovskite cell in Pmmm space group. P0.94BCO has a good chemical compatibility with Ce0.9Gd0.1O1.95 (CGO) electrolyte even at 1000 °C for 24 h. It is observed that the Pr-deficiency can introduce the extra oxygen vacancies in P0.94BCO, further enhancing its electrocatalytic activity for oxygen reduction reaction. P0.94BCO demonstrates the promising cathode performance as evidenced by low polarization are-specific resistance (ASR), e. g. 0.11 Ω cm2 and low cathodic overpotential e. g. −56 mV at a current density of −78 mA cm−2 at 600 °C in air. These features are comparable to those of the benchmark cathode Ba0.5Sr0.5Co0.8Fe0.2O3-δ. The fuel cell CGO-Ni|CGO|P0.94BCO presents the attractive peak power density of 1.05 W cm−2 at 600 °C. Furthermore, the oxygen reduction kinetics of P0.94BCO material is also investigated, and the rate-limiting steps for oxygen reduction reaction are determined.

The characteristics and electrochemical performance of double perovskite EuBaCo 2 O 5+ δ (EBCO) have been investigated as a composite cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The thermal expansion coefficients can be effectively reduced in the case of EBCO-Ce 0.9 Gd 0.1 O 2− δ (CGO) composite cathodes. No chemical reactions between EBCO cathode and CGO electrolyte are observed after sintering at 1000 °C for 24 h. The maximum electrical conductivities of EBCO-CGO materials reach 28-77 S cm −1 with the change of CGO weight ratio from 40 wt. % to 5 wt. %. Among all these components, the EBCO-10 wt. % CGO (EBCO-10CGO) composite cathode gives the lowest area-specific resistance of 0.055 and 0.26 Ω cm 2 in air at 700 and 600 °C, respectively. The maximum power density of Ni-CGO anode-supported single cell consisted of the EBCO-10CGO composite cathode and CGO electrolyte achieves 0.81 W cm −2 at 700 °C. These results indicate that the EBCO-10CGO composite materials can be used as a promising cathode candidate for IT-SOFCs. Furthermore, the rate-limiting steps for the oxygen reduction reaction at the EBCO-10CGO composite cathode interface are determined to be the charge transfer and dissociation of adsorbed molecule oxygen processes.

The layered perovskite PrBaxCo2O5+δ (PBxCO, x = 0.90–1.0) oxides have been synthesized by a solid-state reaction technique, and evaluated as the potential cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). Room temperature X-ray diffraction patterns show the orthorhombic structures which double the lattice parameters from the perovskite cell parameter as a ≈ ap, b ≈ ap and c ≈ 2ap (ap is the cell parameter of the primitive perovskite) in the Pmmm space group. There is a good chemical compatibility between the PBxCO cathode and the Ce0.9Gd0.1O1.95 (CGO) electrolyte at 1000 °C. The electrical conductivity and thermal expansion coefficient of PBxCO are improved due to the increased amount of electronic holes originated from the Ba-deficiency. The results demonstrate the high electrochemical performance of PBxCO cathodes, as evidenced by the super low polarization resistances (Rp) over the intermediate temperature range. The lowest Rp value, 0.042 Ω cm2, and the cathodic overpotential, −15 mV at a current density of −25 mA cm−2, are obtained in the PrBa0.94Co2O5+δ cathode at 600 °C in air, which thus allow to be used as a highly promising cathode for IT-SOFCs. A CGO electrolyte fuel cell with the PrBa0.94Co2O5+δ cathode presents the attractive peak power density of ∼1.0 W cm−2 at 700 °C. Furthermore, the oxygen reduction kinetics of the PrBa0.94Co2O5+δ cathode is also studied, and the rate-limiting steps for oxygen reduction reaction are determined at different temperatures.

In this study, high-quality mesoporous Fe 3 O 4 nanocages (MFONs) have been synthesized by a facile complex-coprecipitation method at 100 °C with addition of triethanolamine and ethylene glycol. The as-prepared Fe 3 O 4 nanocages possess a mesoporous structure and highly uniform dispersion. When used as an anode material for rechargeable lithium-ion batteries, MFONs anode shows high specific capacities and excellent cycling performance at high and low current rates. At a current density of 200 mA g −1 , the discharge specific capacities are 876 mAh g −1 at the 2nd cycle and 830 mAh g −1 at the 100th cycle. Even at the high current density of 1000 mA g −1 , MFONs anode still retains a stable capacity of 573 mAh g −1 after 300 cycles. This superior electrochemical performance is attributed to the unique mesoporous cage-like structure and high specific surface area (133 m 2 g −1 ) of MFONs, which may offer large electrode/electrolyte contact area for the electron conduction and Li + storage. Furthermore, the good mechanical flexibility of the mesoporous nanocages can readily buffer the massive volume expansion/shrinkage associated with the reversible electrode reaction. These results indicate that MFONs can be used as a promising high-performance anode material for lithium-ion batteries.

Owing to unique lamellar nanostructures, 2D inorganic materials are considered as promising candidates in energy storage and conversion. In this paper, a facile two-step synthesis is developed to fabricate 3D hierarchical dual Fe3O4/MoS2 nanosheets (HD-FMNs), in which few-layered MoS2 nanosheets are anchored in 3D Fe3O4 nanosheet network to form the heterojunction structure. Furthermore, it is proved that the synergistic effects on both electron/lithium-ion transport kinetics and mechanical cycling stability benefit from Fe3O4/MoS2 nanosheet incorporation in 3D HD-FMN anode for lithium-ion batteries (LIBs), resulting in the dramatically enhanced performance. The Fe3O4 nanosheet incorporation effectively improves the electronic conductivity due to its half-metal characteristic, while the defect-rich structure in the MoS2 nanosheets can facilitate the lithium ion transport. When tested as potential anode materials, 3D HD-FMNs exhibit a high reversible capacity (650 mAh g−1) at current rate of 5 C (1 C = 1 A g−1) after superior long-term cycles (1000 times), as well as an excellent rate capability even at high current rates. The outstanding electrochemical property of 3D HD-FMNs allows their application in high-performance anode materials for next-generation LIBs. This strategy also opens a new way to design the novel 2D composite materials for electrochemical devices.

International audience; A layered perovskite EuBaCo2O5+δ (EBCO) has been prepared by a solid-state reaction, and evaluated as potential cathode for intermediate-temperature solid oxide fuel cells. Structural characterizations are determined at room temperature using powder X-ray diffraction and transmission electron microscopy technique. The good fits to the XRD data by Rietveld refinement method are obtained in the orthorhombic space group (Pmmm). The lower average thermal expansion coefficient, 14.9 × 10–6 °C–1 between 100 and 800 °C, indicates its better thermal expansion compatibility with conventional electrolytes, compared with the other cobalt-containing cathode materials. The high electrical conductivity and large oxygen nonstoichiometry at intermediate temperatures suggest the effective charge transfer reactions including electron conduction and oxide-ion motion in cathode. As a result, a highly electrochemical activity towards the oxygen reduction reaction is achieved between 600 and 700 °C, as evidenced by low area-specific resistances, e.g. 0.14–0.5 Ω cm2. In addition, cathodic overpotential and oxygen reduction kinetics of the EBCO cathode have also been studied.

International audience; This study is focused on the structural characteristics, oxygen nonstoichiometry, electrical conductivity, electrochemical performance and oxygen reduction mechanism of YBa1−xSrxCo2O5+δ (x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5). The high oxygen nonstoichiometry, δ = 0.18-0.43 at 700 °C, indicates the large oxygen vacancy concentrations in oxides. The electrical conductivity is improved due to the greater amount of electronic holes originated from the increased interstitial oxygen, and the conductivities of all samples are above 100 S cm−1 at 400-700 °C in air. The results demonstrate the promising performance of YBa1−xSrxCo2O5+δ cathodes at intermediate temperatures, as evidenced by low area-specific resistances (ASRs) e.g. 0.21-0.59 Ω cm2 at 700 °C. The lowest ASR, 0.44 Ω cm2, and the cathodic overpotential, −40 mV at a current density of −136 mA cm−2, are obtained in YBaCo2O5+δ cathode at 650 °C. The dependence of polarization resistance on oxygen partial pressure suggests that the charge transfer process is the rate-limiting step for oxygen reduction reaction in YBaCo2O5+δ cathode.

A novel and facile method is applied to successfully synthesize the 20 mol% neodymium-doped ceria (CNO) nanomaterials, including nanowires and nanoparticles, at 240 °C in ambient air. These special nanostructures are easily densified at 1300 °C and provide a three-dimensional (3D), continuous and fast ionic conduction pathway. Surprisingly, the CNO nanomaterials endow the homogeneous and compact ceramics with a competitive ionic conductivity of ∼1.5 S m−1 at 600 °C, down to a pO2 value of about 10−4 atm, and act as a potential electrolyte or composite anode for intermediate-temperature solid oxide fuel cells.

High quality triethanolamine-coated Fe3O4 nanocrystals can be prepared by a novel complex-coprecipitation route based on the use of triethanolamine as ligands to the iron precursors. These nanocrystals show high saturation magnetizations and excellent Cr(VI) removal performances.

Self-assembled magnetite (Fe3O4) peony structures with petal-like nanoslices have been successfully synthesized by a low-temperature and environmentally friendly one-step aqueous method without any surfactant and calcination treatment. Powder X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Mossbauer spectroscopy and superconducting quantum interference device magnetometer measurements were used to characterize the samples. The experimental results indicate that the use of the organic additive triethanolamine (N(CH2CH2OH)3) has an obvious impact on the morphologies of the products. The possible formation mechanism for the Fe3O4 peony structures with well-defined morphology has been presented in detail. The magnetic and electrical properties of the Fe3O4 peony structures are investigated. The sample shows a ferrimagnetic behaviour with a high saturation magnetization of 88.4 emu g−1 at 295 K. Low-field magnetoresistance of ca. −2.0% is achieved in an applied magnetic field of ±1.0 T at 295 K. In addition, the as-prepared Fe3O4 peony materials are studied as adsorbents in waste-water treatment, and exhibit an excellent ability to remove Cr(VI) pollutant from aqueous solution. The Fe3O4 peony sample demonstrates ca. 5.24 mg g−1 of adsorption capacity towards Cr(VI) ions favourably comparing with commercial and reported adsorbents.