A low-temperature solid oxide fuel cell (SOFC) is an attractive new concept, uniquely combining the advantages of relatively low-temperature operation ( 600 8C) and fuel flexibility. [1][2][3][4] Central to this device is the availability of a highly active oxygen reduction reaction (ORR) catalyst. [5][6][7][8] If the operating temperature of the SOFC can be lowered to below 600 8C, it would be more competitive against hydrogenfuelled polymer electrolyte membrane fuel cells, which operate below 200 8C, in terms of reduced system and operation costs, higher theoretical fuel efficiency at decreasing temperature, larger volumetric and gravimetric power densities and similar specific energy (based on liquid hydrocarbons) of SOFCs relative to internal combustion engines. [5,6] Addressing the polarization losses of the SOFC components (e.g., cathode, electrolyte, and anode) at these low temperatures has been the main challenge. For the electrolyte and anode, for example, anode-supported electrolyte, major advances have been demonstrated by fabricating metallic grids supporting a nanometer-thin electrolyte layer [9] and adopting a highly conductive electrolyte consisting of functionally graded bi-layer materials (e.g., Gd-doped CeO 2 /Erdoped Bi 2 O 3 and Sm-Nd-doped CeO 2 /Dy-W-doped Bi 2 O 3 ). [10,11] Therefore, the oxygen reduction reaction (ORR) at the cathode side, rather than ionic conduction in the electrolyte and fuel oxidation at the anode side, is currently limiting the SOFC performance below 600 8C. [12,13] This is reflected in most cathodes by high activation energy for ORR (e.g., thermally activated), which leads to substantial degradation in the ORR properties upon changing the temperature, as well as a relatively high enthalpy of ionic motion, which limits the ORR onset temperature to a high range. [14,15] There has been an ongoing search over the last two decades for a highly active cathode. One of the milestones was a cathode based on mixed ionic-electronic conducting oxides (e.g., oxides featuring simultaneous oxygen-ion and electron transport capabilities). [16,17] A reasonably high ORR performance at 600 8C is afforded by their high ionic and electronic conductivity, which allows the ORR to be extended from the three-phase boundary (for the nonmixed ionic-electronic conductors, or non-MIEC) to the overall surface area of MIEC cathodes. [18] Several cathode compositions, for example, Sm 0.5 Sr 0.5 CoO 3Àd , Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3Àd (BSCF), SrSc 0.2 Co 0.8 O 3Àd , and SrNb 0.1 Co 0.9 O 3Àd , all from the perovskite family, have since been reported that show promising ORR activity at and above 600 8C. [19][20][21][22] Herein, we report a novel perovskite composition, SrSc 0.175 Nb 0.025 Co 0.8 O 3Àd (SSNC), which shows a rapid bulk oxygen diffusion rate below 550 8C, enabling the oxygen reduction reactivity on an SSNC electrode to be enhanced by 100 % at 500 8C relative to the prominent cathode material, BSCF. We also demonstrate, through first-principles calculations, the existence of two oxy...

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A novel cobalt-free and noble metal-free dual-phase oxygen-transporting membrane with a composition of 40 wt % Pr0.6Sr0.4FeO3−δ–60 wt % Ce0.9Pr0.1O2−δ (40PSFO–60CPO) has been successfully developed via an in situ one-pot one-step glycine-nitrate combustion process. In situ XRD demonstrated that the 40PSFO–60CPO dual-phase membrane shows a good phase stability not only in air but also in 50 vol % CO2/50 vol % N2 atmosphere. When using pure He or pure CO2 as sweep gases, at 950 °C steady oxygen permeation fluxes of 0.26 cm3 min–1 cm–2 and 0.18 cm3 min–1 cm–2 are obtained through the 40PSFO–60CPO dual-phase membrane. The partial oxidation of methane (POM) to syngas was also successfully investigated in the 40PSFO–60CPO dual-phase membrane reactor. Methane conversion was found to be higher than 99.0% with 97.0% CO selectivity and 4.4 cm3 min–1 cm–2 oxygen permeation flux in steady state at 950 °C. Our dual-phase membrane - without any noble metals such as Ag, Pd or easily reducible metals oxides of Co or Ni - exhibits high oxygen permeation fluxes as well as good phase stability at high temperatures. Furthermore, the dual-phase membrane shows a good chemical stability under the harsh conditions of the POM reaction and in a CO2 atmosphere at high temperatures.

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We report a novel CO 2 -stable reduction-tolerant dual-phase oxygen transport membrane 40 wt% Nd 0.6 Sr 0.4 FeO 3Àd -60 wt% Ce 0.9 Nd 0.1 O 2Àd (40NSFO-60CNO), which was successfully developed by a facile one-pot EDTA-citric sol-gel method. The microstructure of the crystalline 40NSFO-60CNO phase was investigated by combined in situ X-ray diffraction (XRD), scanning electron microscopy (SEM), back scattered SEM (BSEM), and energy dispersive X-ray spectroscopy (EDXS) analyses. Oxygen permeation and long-time stability under CO 2 and CH 4 atmospheres were investigated. A stable oxygen flux of 0.21 cm 3 min À1 cm À2 at 950 C with undiluted CO 2 as sweep gas is found which is increased to 0.48 cm 3 min À1 cm À2 if the air side is coated with a porous La 0.6 Sr 0.4 CoO 3Àd (LSC) layer. All the experimental results demonstrate that the 40NSFO-60CNO not only shows good reversibility of the oxygen permeation fluxes upon temperature cycling, but also good phase stability in a CO 2 atmosphere and under the harsh conditions of partial oxidation of methane to synthesis gas up to 950 C.