Papers by Keyword: Intermediate Temperature SOFC

Abstract: A high purity of strontium-doped lanthanum cobaltite with formula of La_0.6Sr_0.4CoO_3-δ (LSCO) was synthesized via a combined citrate-EDTA route. LSCO slurry was prepared by mixing LSCO and polyvinyl pyrrolidone (PVP) in ethanol solution. This slurry was manually painted onto both surfaces of yttrium-doped cerate-zirconate, BaCe_0.54Zr_0.36Y_0.1O_2.95 (BCZY) electrolyte to fabricate a symmetrical cell of LSCO|BCZY|LSCO. The scanning electron microscopy (SEM) analysis result revealed that the LSCO was well adhered onto the BCZY electrolyte with no formation of crack or air gap/hole at the LSCO|BCZY interface. Elemental composition of LSCO cathode and BCZY electrolyte elements such as lanthanum (La), barium (Ba) and cerium (Ce) at the interface region was confirmed by electron dispersive spectroscopy (EDS) analysis. The electrochemical performance of the fired cell was analyzed in air by an electrochemical impedance spectroscopy (EIS) as a function of temperature ranging from 500 – 800°C. It is found that the fabricated cell exhibits low polarization resistance (R_p) at the operating temperatures and the values are comparable with those reported in literature. This significant result indicates that LSCO is a promising candidate to be used as a cathode material for BCZY electrolyte at intermediate temperatures.

Abstract: Cermet anode of NiFe(9:1)-La0.9Sr0.1Ga0.8Mg0.2O3 (LSGM) (90:10 weight ratio) was studied for direct CH4 fueled SOFC operating at intermediate temperature. In case of NiFe bimetal anode, power density of the cell decreased drastically after operation under CH4 feeding condition. On the other hand, mixing Sm doped CeO2, MgO, or LSGM is effective for improving the long term stability. The cell with NiFe-LSGM anode exhibited much stable power density under CH4 feeding condition. Deposition of coke was also studied by Raman spectroscopy and no coke deposition was observed after 15 h operation. Since the surface activity of this anode is high, power density was hardly dependent on PCH4.It was found that NiFe-LSGM10 shows a high tolerance against the coke deposition under CH4 feeding condition.

Abstract: In this study we present the preparation of SOFC half cells by electrophoretic deposition. The cathode is deposited from a methyl ethyl ketone (MEK) suspension on dense apatite type lanthanum silicate (ATLS) pellets using a constant voltage. ATLS are a new class of electrolytes, which provides good oxygen permeability even at temperatures below 800°C. As cathode materials we used La2Ni0.8Cu0.2O4+δ (LNC) and La0.8Sr0.2Ni0.6Fe0.4O3 (LSNF). A conductive layer on the ATLS material was used to provide the necessary conductivity for electrophoretic deposition (EPD) process. For the preparation of suitable suspensions the charging behaviour and particle size of the different powders were investigated by means of zeta-potential and laser scattering measurements. When the electrophoretic mobility of the suspended particles was not sufficient iodine was added. Deposition kinetics were determined prior to preparation of the half cells. EPD parameters as well as sintering conditions were optimized in order to gain well adhering porous cathode layers.

Abstract: Effects of various additives to Ni anode on SOFC using La0.9Sr0.1Ga0.8Mg0.2O3 based oxide were investigated in this study. Among the examined additives, it was found that the addition of small amount of Fe is highly effective for increasing the anodic activity. When 5 wt% Fe was added to Ni anode, the anodic overpotential was as small as 34 mV at 873 K, 0.1A/cm2, which is almost half of pure Ni anode. Since the estimated activation energy for anodic reaction decreased, addition of Fe to Ni seems to be effective for increasing the activity of Ni for anodic reaction. XRD measurement after power generating property suggests that added Fe was formed alloy with Ni. SEM observation shows the high dispersion of Ni metal was sustained by addition of small amount of Fe. Consequently, this study reveals that Ni-Fe bimetal is highly active for anodic reaction of SOFCs at decreased temperature.

Abstract: Intermediate temperature SOFC components, such as dense, nanostructured SDC electrolytes (samarium doped ceria) and porous anode sublayers were fabricated by suspension plasma spraying using an axial feed dc plasma torch. The liquid carrier employed in this approach allowed for controlled injection of much finer particles than in conventional thermal spraying, leading to thin coatings with a refined microstructure. Dense, thin (<10(m) and non-fractured electrolytes were created. Various processing routes for SOFC half-cells, using tape-cased, plasmasprayed and suspension-sprayed anodes, were explored. Loss of integrity and non-continuous coverage of the anode constituted the principal difficulties in the subsequent electrolyte deposition. The role of suspension feedstock particle size is discussed. Amongst various schemes investigated, a processing route that employs sequential suspension plasma spraying steps for both the electrolyte and the anode, using relatively large primary particles in the feedstock, constituted the most promising approach.