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Abstract: A palladium-impregnated La0.75Sr0.25Cr0.5Mn0.5O3−δ /yttria-stabilized zirconia (LSCM/YSZ) composite anode is investigated for the direct utilization of methane and ethanol fuels in solid oxide fuel cells (SOFCs). Impregnation of Pd nanoparticles significantly enhances the electrocatalytic activity of LSCM/YSZ composite anodes for the methane and ethanol electrooxidation reaction. At 800°C, the maximum power density is increased by two and eight times with methane and ethanol fuels, respectively, for a cell with the Pd-impregnated LSCM/YSZ composite anode, as compared with that using a pure LSCM/YSZ anode. No carbon deposition is observed during the reaction of methane and ethanol fuels on the Pd-impregnated LSCM/YSZ composite anode. The results show the promises of nanostructured Pd-impregnated LSCM/YSZ composites as effective anodes for direct methane and ethanol SOFCs. [Copyright &y& Elsevier]

Abstract: (La0.6Ba0.4)(Co0.2Fe0.8)O3 (LBCF) is synthesized by a sol–gel method as a Cr-tolerant cathode for intermediate-temperature solid oxide fuel cells (ITSOFCs). The electrochemical performance and Cr deposition process for the O2 reduction reaction on LBCF cathodes in the presence and absence of a Fe–Cr alloy interconnect are investigated in detail, in comparison with a (La,Sr)(Co,Fe)O3 (LSCF) electrode. Cr deposition occurs for the O2 reduction reaction on LBCF electrodes in the presence of Fe–Cr alloy. Very different from that observed for the reaction on the LSCF cathode, Cr deposition on the LBCF electrode/gadolinia-doped ceria (GDC) electrolyte system is very small and shows little poisoning effect for O2 reduction on LBCF electrode. The results demonstrate that the LBCF electrode has a high resistance towards Cr deposition and high tolerance towards Cr poisoning. [Copyright &y& Elsevier]

Abstract: The crystalline structure, redox stability and electrical conductivity of LaCrO3, (La1−x M x )CrO3 (M=Mg, Ca, Ba for x =0.3 and M=Sr for x =0.25), and (La0.75Sr0.25)(Cr0.5Mn0.5)O3 (LSCM) perovskites are studied from 500 to 800°C in both oxidizing and reducing atmospheres. Dopability, redox stability and electrical conductivity are compared and examined. A-site doping with alkaline elements is found to improve significantly the electrical conductivity, particularly if properly doped. The highest conductivity is obtained with Ca- and Sr-doped LaCrO3. A-site doping also reduces the activation energy of the electrical conductivity, particularly under a reducing environment. Preliminary electrochemical results indicate that Ca-doped LaCrO3 shows promise as a cathode for solid oxide fuel cells. [Copyright &y& Elsevier]

Abstract: Oscillation of open circuit potential (OCP) and potential is observed for the methane oxidation reaction on (La0.75Sr0.25)(Cr0.5Mn0.5)O3 (LSCM) and LSCM/YSZ composite electrodes of solid oxide fuel cells (SOFCs) in weakly humidified methane (i.e., 97%CH4/3%H2O). In dry methane (i.e., 100%CH4), the potential oscillation is reduced significantly. The oscillation behaviour of OCP is also found to be strongly related to the temperature, the microstructure of the composite electrode and the fuel composition. The results indicate that the potential oscillation is thermally activated and is most likely associated with the adsorbed oxygen species on the electrode surface. [Copyright &y& Elsevier]

Abstract: Oxygen reduction on a Sr-doped LaMnO3 (LSM) electrode of a solid oxide fuel cell (SOFC) is investigated in the absence and the presence of a Fe–Cr alloy interconnect. The results show that oxygen reduction is controlled by a surface exchange reaction that involves dissociative adsorption and diffusion of oxygen on the LSM electrode surface, and migration of oxygen ions from the LSM to the yttria stabilized zirconia (YSZ) electrolyte lattice at the three-phase boundary (TPB). In the presence of Fe–Cr alloy, the reaction order and activation energy of the surface exchange process are similar to those in the absence of Fe–Cr alloy. This indicates that the presence of gaseous chromium species simply reduces the active sites for the surface exchange reaction by blocking oxygen vacancy formation on the LSM electrode surface. On the other hand, the Cr2O3/(Cr,Mn)3O4 solid species deposited on the YSZ electrolyte surface primarily inhibits the migration of oxygen ions into the YSZ electrolyte, as indicated by a significant increase in the activation energy of the migration process of the oxygen ions into YSZ electrolyte. [Copyright &y& Elsevier]

In solid oxide fuel cells (SOFCs), chromium deposition and poisoning of metallic interconnect is one of the most important issues in the electrochemical activity and stability of the cathode for the oxygen reduction reaction (ORR). In this paper, the chromium evaporation characteristics, oxide scale growth, and deposition of chromium on the ORR on (La,Sr)MnO 3 (LSM) cathode are studied at 700–800 °C for SUS430 alloy interconnect material in the intermediate-temperature solid oxide fuel cells. The chromium vaporization rate is measured using the transpiration technique and the surface morphologies, and cross-sections of oxide scales are examined by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The results indicate that chromium volatilization is correlated with the composition and morphology of the oxide scale, the Cr volatilization process presents two stages according to the structural evolution of the oxide scale. In addition, deposition and poisoning of Cr species released from metallic interconnect on the LSM cathode are studied and the formation of MnCr 2 O 4 phase on the LSM backbone degrades the ORR electrochemical activity, causing the increase of overpotential of the cathode. The results obtained give insight into the mechanism of the Cr poisoning effect in intermediate-temperature. [Display omitted] • Chromium volatilization is correlated with the composition of the oxide scale. • The amount of chromium volatilization increases with the temperature. • The deposition of Cr species deteriorates the ORR activity of the cathode. [ABSTRACT FROM AUTHOR]

Abstract: Anode-supported planar solid oxide fuel cells (SOFCs) with an active area of 81cm2 (9cm×9cm) and nano-structured La0.6Sr0.4Co0.2Fe0.8O3−δ +Y2O3 stabilized ZrO2 (LSCF+YSZ) composite cathodes are successfully fabricated by tape casting, screen printing, co-firing and solution impregnation, and tested using H2 fuel and air oxidant at various flow rates. Maximum power densities of 437 and 473mWcm−2 are achieved at 750°C by loading 0.6 and 1.3mgcm−2 of LSCF in the composite cathodes, respectively. The gas flow rates, particularly the air, have a significant effect on the cell performance. Cell performance degradation with time is also observed, which is considered to be associated with the growth and coalescence of the nanosized LSCF particles in the composite cathode. The use of the LSCF cathode in combination with YSZ electrolyte without a Gd-doped CeO2 (GDC) buffer layer is proved to be applicable in large cells, even though the thermal stability of the nanosized LSCF needs to be further improved. [Copyright &y& Elsevier]

Abstract: Chromium-deficient Nd0.75Ca0.25Cr1−x O3−δ (0.02≤ x ≤0.06) oxides are synthesized and assessed as a novel ceramic interconnect for solid oxide fuel cells (SOFCs). At room temperature, all the samples present single perovskite phase after sintering at 1600°C for 10h in air. Cr-deficiency significantly improves the electrical conductivity of Nd0.75Ca0.25Cr1−x O3−δ oxides. No structural transformation occurs in the Nd0.75Ca0.25Cr1−x O3−δ oxides in the temperature range studied. Among all the samples, the Nd0.75Ca0.25Cr0.98O3−δ sample with a relative density of 96.3% exhibits the best electrical conductivity of 39.0 and 1.6Scm−1 at 850°C in air and hydrogen, respectively. The thermal expansion coefficient of Nd0.75Ca0.25Cr0.98O3−δ sample is 9.29×10−6 K−1 in the temperature range from 30 to 1000°C in air, which is close to that of 8mol% yttria stabilized zirconia electrolyte (10.3×10−6 K−1) and other cell components. The results indicate that Nd0.75Ca0.25Cr0.98O3−δ is a potential interconnect material for SOFCs. [Copyright &y& Elsevier]

Abstract: La0.8Sr0.2Co0.5Fe0.5O3−δ (LSCF) cathodes infiltrated with electrocatalytically active Pd and (Gd,Ce)O2 (GDC) nanoparticles are investigated as high performance cathodes for the O2 reduction reaction in intermediate temperature solid oxide fuel cells (IT-SOFCs). Incorporation of nano-sized Pd and GDC particles significantly reduces the electrode area specific resistance (ASR) as compared to the pure LSCF cathode; ASR is 0.1Ωcm2 for the reaction on a LSCF cathode infiltrated with 1.2mgcm−2 Pd and 0.06Ωcm2 on a LSCF cathode infiltrated with 1.5mgcm−2 GDC at 750°C, which are all significantly smaller than 0.22Ωcm2 obtained for the reaction on a conventional LSCF cathode. The activation energy of GDC- and Pd-impregnated LSCF cathodes is 157 and 176kJmol−1, respectively. The GDC-infiltrated LSCF cathode has a lower activation energy and higher electrocatalytic activity for the O2 reduction reaction, showing promising potential for applications in IT-SOFCs. [Copyright &y& Elsevier]

A comparative study is carried out on the effect of nano-sized and micron-sized Y2O3/ZrO2 (YSZ) powders on the fabrication and performance of anode-supported solid oxide fuel cells. It is found that pellets made of nano-sized YSZ powder can achieve a relative density of 96% at a sintering temperature of 1400 °C and 92% at sintering temperature as low as 1200 °C. For pellets made of micron-sized YSZ powder, densification only occurred at a sintering temperature of 1400 °C. On co-sintering the nano-sized YSZ electrolyte film with the anode support/substrate, the electrolyte is unable to sinter fully at 1400 °C, but forms a porous structure which leads to a reduced open-circuit potential and poor cell performance. This is most likely due to the nano-sized YSZ electrolyte thin film having a very low green density and there being a significant difference in the sintering behaviour of the YSZ thin layer and the Ni/YSZ cermet substrates. The sintering behaviour and the nature of YSZ powders exert a significant effect on the fabrication and performance of Ni/YSZ anode-supported thin YSZ electrolyte cells. [Copyright &y& Elsevier]