Energy storage technology plays a critical role in integrating variable energy sources into the grid and ensuring energy consistency. Electrochemical supercapacitors are one of the most promising energy storage devices, as they present multiple advantages of high power density, rapid charge/discharge characteristics, and long‐term cycle stability. Herein, the NiCo 2 O 4 /molybdate nanocomposites are developed as electrode materials for supercapacitor applications. The NiCo 2 O 4 /molybdate nanocomposites are synthesized by a facile single‐pot hydrothermal method and are coated on a carbon cloth substrate to form flexible supercapacitor electrodes. The structures, chemical compositions, morphologies, and textural properties of these materials are carefully studied by X‐Ray diffraction, X‐Ray absorption spectroscopy, scanning electron microscopy/energy‐dispersive X‐Ray spectroscopy mapping, and N 2 adsorption–desorption isotherms. The formation of spinel NiCo 2 O 4 nanorods decorated with molybdate (AMoO 4 , A = Co, Ni) particles is confirmed for all samples. The NiCo 2 O 4 /CoMoO 4 electrode exhibits pseudocapacitive behavior and provides the highest specific capacitance (287.28 F g −1 at current density 6 A g −1 ), about 5.5 times as high as that of NiCo 2 O 4 , with excellent cycle stability (107% specific capacitance retention after 1000 charge/discharge cycles at 1 A g −1 ). Therefore, the NiCo 2 O 4 /CoMoO 4 composites can be considered as a promising pseudocapacitor electrode material.

Metal-Supported Solid Oxide Fuel Cells (MS-SOFCs) have gained significant interest due to their potential advantages (low-cost, tolerance to redox and thermal cycling, robust and manufacturing) over conventional fuel cells. This work focuses on studying corrosion and electrical conductivity of porous metallic supports (stainless steel 316L and FeCrAl alloy) under different temperatures and atmospheres considering physical, chemical and electrical characterizations. Within the studied operating temperature range (500 °C–700 °C), the FeCrAl support resists to corrosion under air and H2. At temperatures higher than 700 °C it forms a layer of alumina. The FeCrAl resistivity generally remains stable under H2 and slowly increases under air. In contrast, the 316L support is only stable at 500 °C under air and at 500 °C and 600 °C under H2. Above these temperatures, the 316L support shows severe corrosion. The resistivity is stable up to 600 °C, increases strongly for the support under air and slightly for the support under H2 with the temperature increase.

Single crystals and powders of the orthophosphates Ag2Mg2Fe(PO4)3 with A = Na+ or Ag+ have been synthesized by solid-state reaction. The X-ray diffraction diagrams of Na2Mg2Fe(PO4)3 and Ag2Mg2Fe(PO4)3 were refined by pattern matching method. The two compounds crystallize in C2/c space group adopting the alluaudite type structure. Refinement of the crystal structure of the silver-containing compound leads to the non-stoichiometric chemical formula Ag1.67Mg2.33Fe0.89(PO4)(3) while that of the sodium-containing compound leads to the stoichiometric chemical formula Na2Mg2Fe(PO4)(3). The complex impedance plots are obtained in frequency range from 0.1 Hz to 1 MHz, between 573 K and 823 K Na2Mg2Fe(PO4)(3) presents a conductivity of 0.25 x 10(-5) S cm(-1) at 773 K, with Ea = 0.81 eV. For Ag2Mg2Fe(PO4)(3), a better ionic conductivity of 1.8 x 10(-3) S cm(-1) has been observed at the same temperature with Ea = 0.47 eV. The two alluaudite compounds present an intrinsic cationic conductivity type resulting from Na+ or Ag+ ions movement.

The electrochemical performance of La0.5Sr1.5MnO4 +/-delta (L5S15M) as SOFC cathode was studied using Electrochemical Impedance Spectroscopy (EIS) measurements. The influence of the sintering temperature on the electrochemical performance was examined in air for Au/L5S15M/GDC/YSZ/GDC/L5S15M/Au symmetrical cell. For the oxygen reduction reaction, the electron transfer between the electrode and oxygen, and the incorporation of oxygen ions into the electrode are the main controlling processes of oxygen reduction reaction for electrodes sintered at 1150 and 1200 degrees C. Increasing the sintering temperature up to 1250 degrees C increases the Sr diffusion through GDC interlayer, which leads to Sr accumulation at the GDC/YSZ interface with SrZrO3 formation and subsequent cell performance degradation. The lowest area specific resistance (ASR) values was obtained for the L5S15M electrode sintered at 1150 degrees C. (C) 2019 Elsevier Ltd. All rights reserved.

La4BaCu5-xMnxO13+delta materials have been synthesized by the sol-gel method in air and studied as possible electrode materials for symmetrical Solid Oxide Fuel Cells (S-SOFC). Within the series, La4BaMn5O13+delta (LBMn) exhibits an excellent stability in reducing atmosphere and remarkable redox stability, although a structure transition from rhombohedral to cubic perovskite structure is found beyond 500 degrees C in air or wet diluted hydrogen. The thermal expansion coefficients (TEC), deduced from HT-XRD study during redox cycling, make the manganite compatible with classical SOFC electrolytes at low temperature; however, relatively high values of 15.8(5) and 18.1(2) K-1 are found in cathode and anode conditions for T > 500 degrees C. With high electrical conductivities of 178 and 33.3 S cm(-1), in air and hydrogen at 800 degrees C, we demonstrate that the La0.8Ba0.2MnO3 +/-delta manganite fulfils all the preliminary requirements of an electrode material for symmetrical SOFC.

The possibility to use bilayer electrolytes based on bismuth oxide conductors should lead to a drastic decrease of solid oxide fuel cell (SOFC) operation temperature and calls for a reevaluation of some of the parameters optimized for high temperature applications. In this work we reinvestigate the promising La1-xSrxMnO3/Bi1.5Er0.5O3 (LSM/ESB) composite electrodes, varying the strontium content from x similar to 0.2, the typical high temperature LSM composition, to evaluate the optimum composition. Increasing the strontium content up to x = 0.4-0.5 leads to a 14% decrease of the activation energy, resulting in a 50% decrease in the polarization resistance of symmetric cells at 500 degrees C compared to the traditional La0.85Sr0.15MnO3 composition with similar microstructure. The electrode performance is deteriorated by further increase in the strontium content. Based on surface composition, investigated by low energy ion scattering, we show that the SrO surface segregation proposed as the main deterioration mechanism for LSM based HT-SOFC is not an issue below 800 degrees C. Furthermore, we propose that the increase in performance is related to the decrease of cationic vacancies in LSM observed for high strontium content, which may help the oxygen dissociation and surface transport.

La4BaCu5-xCoxO13+delta system was successfully synthesized by a modified Pechini route in air. A structural phase transition is observed along the series, from tetragonal ordered structure for 0 <= x <= 2 to a rhombohedral disordered perovskite for x = 5. A TEC value of 17.3 x 10(-6) K-1, was found by High-Temperature X-ray Diffraction (HT-XRD) in air for La4BaCu5-xCoxO13+delta. The conductivity of La4BaCu5-xCoxO13+delta increases with temperature reaching a maximum of 778 S cm(-1) at 405 degrees C in air followed by a decrease with further increase in temperature with values of 600-664 S cm(-1). The cathode polarization resistance of La4BaCu5-xCoxO13+delta evaluated in air at 750 degrees C is 0.34 Omega cm(2) with an activation energy of 1.65 eV. These results demonstrate the possible use of La4BaCu5-xCoxO13+delta materials as cathode for Intermediate-Temperature Solid Oxide Fuel Cell (IT-SOFC).

The Ruddlesden Popper (RP) manganites LaxSr2-xMnO4 +/-delta with compositions 0.25 <= x <= 0.6 have been successfully synthesized as single phases by solid-state reaction in air. All those materials are not only stable in reducing atmosphere but they also maintain the K2NiF4-type structure with I4/mmm symmetry under redox cycling conditions with limited volume changes. The x = 0.5 phase was analyzed by in situ high temperature neutron powder diffraction (HTNPD), under flowing hydrogen, showing the formation of oxide-ion vacancies on the equatorial sites of the perovskite planes, during reduction process. The total electrical conductivity was optimized and found maximum for x = 0.5 with values of 35.6 S cm(-1) and 1.9 S cm(-1) at 800 degrees C in air and 3% H-2/Ar, respectively, what is judged to be sufficient for an active layer of symmetrical SOFC electrode. First Electrochemical Impedance Spectroscopy (EIS) measurements in both oxidizing and reducing conditions, using an YSZ electrolyte and a GDC buffer layer, are presented giving rise to promising values. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

The thermoelectric material Ca3Co4O9+δ (CCO), with an electronic conductivity of σe=240S·cm−1 at 650°C and a good chemical and mechanical compatibility with the standard Ce0.9Gd0.1O1.95 electrolyte (CGO, TEC: 9–10·10−6K−1), was recently identified as a potential cathode material for solid oxide fuel cells. In this contribution the electrochemical properties of a series of CCO-CGO composite cathodes were studied as function of composition and layer thickness in a symmetrical cell set-up. The cathodes were applied on both sides of a CGO electrolyte by screen-printing. The cathode thickness was controlled through repeated drying-screen-printing cycles and the cathode compositions varied from 80‐20 to 30-70wt.% of CCO/CGO. The lowest area specific resistance (ASR) was obtained for the CCO50–50 composition with 3 layer applications (21μm thickness) with an ASR of 0.5Ω·cm2 at 700°C. All electrode impedances could be modelled successfully with an LR(RQ)(RQ)G(RC) circuit yielding a pseudo-χCNLS2 of 1–8·10−7, which indicates an excellent fit (‘G’ denotes a Gerischer element). The fit-parameters showed quite consistent behaviour as function of temperature, composition and cathode thickness. The CNLS-analysis of thickness dependence showed that almost the entire cathode layer is electrochemically active. The oxygen reduction reaction is mainly governed by three processes, diffusion process at high frequency being the most limiting step.

Stoichiometric and sub-stoichiometric lanthanum barium titanates (LBT) of perovskite structure type, substituted or not with Mn and/or Ce at the Ti-site, were prepared by sol–gel route with heat treatment in air. All the compounds display a cubic Pm-3m symmetry, which remains stable in reducing atmosphere. Whereas Mn substitution highly promotes the reducibility of the material, the electrical and electrochemical performance of Mn-doped compounds is decreased with respect to non-doped sub-stoichiometric LBT. In contrast, the electrical conductivity and resistance polarization of Ce-substituted LBT are close to those of non-doped LBT and Ce-substituted LBT appears especially efficient in improving the catalytic properties for methane steam reforming and avoiding carbon formation.