The use of a single porous mixed ion-electron conducting (MIEC) material as both the oxygen and fuel electrodes in reversible solid oxide cells is of increasing interest, primarily due to the resulting simplified cell design and lower manufacturing costs. In this work, La(0.3)Sr(0.7)Fe(0.7)Cr(0.3)O(3-δ) (LSFCr-3) was studied in a 3-electrode half-cell configuration in air, pure CO2 and in a 1 : 1 CO2 : CO mixture, over a temperature range of 650-800 °C. A detailed analysis of the impedance (EIS) data, under both open circuit and polarized conditions, as well as the cyclic voltammetry response of LSFCr-3 has shown that it is very active in all of these environments, but with oxygen evolution being somewhat more facile that oxygen reduction, and CO2 reduction more active than CO oxidation. Evidence for a chemical capacitance, associated with the Fe(3+/4+) redox process in LSFCr-3, was also obtained from the EIS and CV data in all gas environments.

Redox stable SOFCs with Ni-YSZ cermet anodes were developed for electrolyte supported design (electrolyte thickness: 170 μm). Redox stable Ni-YSZ anode was prepared by infiltrating polymeric NiO precursor into pre-sintered porous YSZ layer (∼10 μm thick) followed by reduction ex situ. Polymeric precursor infiltration technique yielded a Ni-YSZ cermet microstructure with nanosized Ni particles coating the surface of porous YSZ. Low temperature processing of nanostructured Ni-YSZ cermet resulted in the reduction of internal stresses between Ni/NiO coating and YSZ skeleton during the redox cycling process. Electrolyte supported SOFC prepared with Ni-infiltrated anode showed a power density of ∼0.315 Watt.cm −2 and a highly redox stable anode (reduction of power density less than 1% after 15 redox cycles) in humidified forming gas (10%H 2 -90%Ar).Solid oxide fuel cells (SOFCs) are promising energy conversion devices due their high efficiency and fuel flexibility. Typical SOFCs use Ni-YSZ cermet as anode and LSM-YSZ composite as cathode with YSZ (Yttria-Stabilized Zirconia) electrolyte. Ni-YSZ cermet is an attractive anode material due to the fact that it provides low ohmic and polarization resistances at operational temperatures (600-1000 • C). Commonly, Ni-YSZ cermet is prepared by co-sintering a mixture of NiO and YSZ powders at high temperatures (1300-1450 • C), followed by ex situ reduction in fuel (e.g. hydrogen) at 800 • C. 1 During long term operation, it is expected that the SOFC will go through several redox (reduction-oxidation) cycles due to intentional or erroneous interruption of fuel supply. 2 Therefore, it is of great importance that the Ni-YSZ cermet withstands several redox cycles in order for SOFCs to be viable for long term operation. However, the initial performance of the fuel cell is generally not recovered after redox cycling due to the mechanical failure of Ni-YSZ cermet. The internal stresses caused by the expansion of Ni upon oxidation crack the YSZ in the cermet structure. 3-5 This causes a severe degradation in performance and even destruction of the electrolyte in configurations with thin electrolytes. 6,7 One of the approaches to obtain redox stable anodes is replacing Ni with ceramic materials that are redox stable by nature and electronically conductive in reducing atmospheres. 7-11 On the other hand, significant effort was focused on the understanding of the redox behavior of Ni/NiO and the modification of the standard Ni-YSZ cermet accordingly. These modifications include the variation of Ni content and grain size, introduction of a buffering interlayer, using 3 mol% YSZ for improved mechanical strength and addition of dopants to the structure. 4,5,[12][13][14] Considering the fact that the degradation of Ni-YSZ cermet processed at temperatures above 1300 • C is caused by mechanical stresses associated with the Ni phase, low temperature processing techniques, such as infiltration into pre-sintered porous YSZ skeleton was proposed. 15,16 It was reported that the conductivity of the Ni...

The long term performance of SOFC with nanocomposite Ni-YSZ anode and LSM-YSZ cathode was reported. The SOFC was prepared by infiltrating polymeric precursors of NiO and LSM from anode and cathode sides respectively. The fuel cell showed relatively high initial performance (0.49 Watt/cm 2 at 800 • C) for the given electrolyte thickness (∼170 μm). Long term stability tests showed that the power density dropped to 0.41 Watt/cm 2 in the first 60 hours of operation in short circuit conditions and no further change in the power density was observed. Low electrode polarization resistance was obtained (∼0.080 Ohm.cm 2 for combined anode and cathode at 800 • C) which showed no significant change with prolonged time. The slight drop in power density was related to the change in ohmic resistance which was attributed to the increase in current collection resistance. The fact that the majority of the resistance was due to the electrolyte resistance (∼80%) suggests that stable SOFCs with high power densities could be achieved with thinner electrolytes. After >100 hours of operation at 800 • C in short circuit conditions, the fuel cell was measured at higher temperatures. Power densities were 0.71 Watt/cm 2 and 1.0 Watt/cm 2 at 900 • C and 1000 • C, respectively.

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A novel technique based on polymeric precursor infiltration into porous layers was developed to process composite materials as highly efficient cathode/current collector structures for solid oxide fuel cells (SOFCs). Powder based Pt and YSZ inks were used to form porous cathode/current collector layers on electrolyte supported symmetrical structures that were infiltrated with polymeric LSM precursor. Electrochemical testing of the samples was performed by impedance spectroscopy techniques. Polarization resistance of the cathode was as low as 0.022 Ohm.cm 2 at 800 • C demonstrating the potential of fabricating highly efficient cathodes. Infiltration process led to a stable composite of the cathode/current collector structures, ensuring a high current collection efficiency and long term stability at operational temperatures.La 1−x Sr x MnO 3 (LSM) is a mixed ionic and electronic conductor widely used in high temperature solid oxide fuel cells (SOFCs) with Yttria stabilized Zirconia (YSZ) electrolytes. 1 Relatively low ionic conductivity of LSM is generally compensated by mixing with YSZ. This way, the oxygen gas molecules that are reduced to oxygen ions by the catalytically active LSM sites are collected and transported to the electrolyte and finally to anode reaction sites. 2 Most commonly used technique to fabricate LSM-YSZ composites is screen printing of powder based inks and co-sintering at temperatures between 1100 • C and 1200 • C. 3, 4 However, both components have different sintering rates; therefore controlling microstructural development becomes more challenging. For instance, in order for YSZ to be ionically conductive, sintering temperatures of at least 1150 • C are necessary which results in a density about 50% of its theoretical density. 5 On the other hand, at similar temperatures, LSM sinters typically up to 90% of its theoretical density. 6 Consequently, YSZ particles stay disconnected at low co-sintering temperatures (less than 1100 • C) and high co-sintering temperatures result in over densification of LSM, which, in turn, leads to reduced YSZ-LSM interfacial area. In addition, formation of La 2 Zr 2 O 7 phase at YSZ-LSM interface at sintering temperatures above 1100 • C has been reported to degrade the performance and stability of YSZ and LSM based composite cathodes. 1,7,8 In previous studies, various attempts were made to determine the optimum process parameters including LSM -YSZ solids loading, particle size ratios, sintering temperatures and sintering additives. 3,4,7,9 These investigations resulted in lower cathode polarization resistances of 0.

SiO2-TiO2 thin films for use as fiber optic guiding layers of optical DNA biosensors were fabricated by the sol-gel dip coating technique. The chemical structure and the surface morphology of the films were characterized before immobilization. Single probe DNA strands were immobilized on the surface and the porosity of the films before the hybridization process was measured. Refractive index values of the films were measured using a Metricon 2010 prism coupler. On the surface of each film, 12 different spots were taken for measurement and calculation of the mean refractive index values with their standard deviations. The increased refractive index values after the immobilization of single DNA strands indicated that immobilization was successfully achieved. A further refractive index increase after the hybridization with target single DNA strands showed the possibility of detection of the E. coli O157:H7 EDL933 species using strands of 20-mers (5′-TAATATCGGTTGCGGAGGTG -3′) sequence.

Infiltration of a polymeric nickel oxide precursor into a sintered porous ytrria -stabilized zirconia (YSZ) skeleton is a promising approach to achieve redox stable solid oxide fuel cells. In order to ensure that the porous YSZ skeleton was mechanically strong enough to withstand the stresses caused by the volumetric expansion of the Ni phase upon oxidation even at relatively high loadings, a polymeric YSZ precursor was infiltrated into to the porous YSZ skeleton, prior to NiO infiltration. It was shown that infiltration of YSZ precursor strengthened the porous YSZ skeleton without compromising from the porosity or initial YSZ particle size significantly. The amount of infiltrated YSZ and the subsequent heat-treatment temperature were determined to be important processing parameters in achieving redox stable Ni-YSZ anodes. Electrolyte supported SOFC (electrolyte thickness ∼ 180 μm) with redox stable anode prepared by YSZ and NiO infiltrations showed a power density of ∼0.41 Watt/cm 2 at 800 • C which did not change significantly after 20 redox cycles in 10%H 2 -90% Ar fuel. Impedance spectroscopy measurements at 800 • C showed significantly low electrode polarization resistances (anode + cathode ∼ 0.07 Ohm.cm 2 at 800 • C) which remained stable upon redox cycling.

Long-term electrochemical performance of polymeric precursor-derived films of LaCoO 3 doped with Ca 2+ (LCC), instead of the larger Sr 2+ which segregates at the electrode surface forming oxides/hydroxides, was investigated in the present study. It was determined that pre-calcination at 800 °C (LCC02-800) resulted in a higher electrochemical performance but a poorer long-term stability than those pre-calcined at 700 °C (LCC02-700) or 900 °C (LCC02-900). Increasing Ca 2+ content (LCC04-800) enhanced the initial electrochemical performance slightly, while causing a much poorer long-term stability. Microstructural evolution analyses revealed that, although it had some impact on the initial and long-term performance of LCC electrodes, it was not the strongest influence. It was determined via XPS analyses that formation of CaO and CaO + La 2 O 3 layers at the LCC02-800 and LCC04-800 surfaces, respectively, accompanied by a decrease in the relative amounts of adsorbed oxygen species (corresponding to surface oxygen vacancies) caused a faster performance degradation in these samples than those pre-calcined at 700 or 900 °C. Eventually, only the surface cation ratio of LCC02-700 became close to the theoretical one after long-term operation.