Composite cathode materials Ag-Ba0.5Sr0.5Co0.8Fe0.2O3 for solid oxide fuel cells

Abstract

Silver-Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ (BSCF) cathodes were prepared in two ways. In the first method, Ag-BSCF composite powder was prepared in ethanol solution, where Ag nanoparticles serving as a component in the preparation of Ag-BSCF composite cathodes had been previously obtained via one-step synthesis in absolute ethanol using a neutral polymer (polyvinylpyrrolidone). To the best of our knowledge, this is the first study to use a Ag sol obtained by the above method for preparation of Ag-BSCF composite powder. Then, a paste containing this powder was screen-printed on a Sm 0.2 Ce 0.8 O 1.9 electrolyte and sintered at 1,000°C. In the second technique, an aqueous solution of AgNO 3 was added to a previously sintered BSCF cathode, which was then sintered again at 800°C. The oxygen reduction reaction at the quasi-point BSCF cathode on the Sm 0.2 Ce 0.8 O 1.9 electrolyte was tested by electrochemical impedance spectroscopy at different oxygen concentrations in three electrode setup. The continuous decrease of polarization resistance was observed under polarization −0.5 V at 600°C. The comparative studies of both obtained composite Ag-BSCF materials were performed in hydrogen-oxygen IT-SOFC involving samariadoped ceria as an electrolyte and Ni-Gd 0.2 Ce 0.8 O 1.9 anode. In both cases, the addition of silver to the cathode caused an increase in current and power density compared with an IT-SOFC built with the same components but involving a monophase BSFC cathode material.

Thermal shock resistant composite cathode material Sm0.5Sr0.5CoO3–δ–La0.6Sr0.4FeO3–δ for solid oxide fuel cells

“…Only a 2 mA decrease in absolute value of current is observed during the initial 30 h. It means that no unfavorable phenomena, which might lead to the deterioration of the cathode performance, occurred at least during the first 30 h. That behavior is opposite to the trend reported by Gao et al [4] for SSCCe 0.85 Sm 0.075 Nd 0.075 O 2−δ (SNDC) composite, by Mosiałek et al for BSCF [23], and by Wang and Jiang [49] for LSM.…”

“…5d in [23]). SDC electrolyte disks of 20 mm diameter and 1 mm thickness were prepared as described elsewhere [24].…”

Silver migration at the Ag|Sm0.2Ce0.8O1.9 interface

“…The SDC electrolytes were prepared as described in [26]. Wires made of 99.99 % silver, with a diameter of 0.5 mm, were supplied by Mennica Polska S.A. La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) paste (Fuel Cell Materials) was screen-printed onto the SDC surface, which was then fired for 2 h at 1,100°C with a heating and cooling rate of 1°C min .…”

Ba0.5Sr0.5Co0.8Fe0.2O3–δ–La0.6Sr0.4Co0.8Fe0.2O3–δ Composite Cathode for Solid Oxide Fuel Cell

“…The good cathode material should reveal excellent catalytic activity in the oxygen reduction reaction (ORR), high ionic and electronic conductivity and the thermal expansion coefficient (TEC) similar to the TEC of the electrolyte. (BSCF) cathode materials are extensively studied due their excellent properties [1][2][3][4][5][6][7][8][9][10]. The electronic conductivity of LSCF is very high in comparison to other cathode materials, revealing the maximum value of 215.58 S cm −1 at 823 K, whereas BSCF reveals much lower electronic conductivity 14.87 S cm −1 at 773 K [1].…”

“…LSCF at 1073 K reveal ionic conductivity at the same level as gadolinia-doped ceria (GDC) [2], whereas ionic conductivity of BSCF is even higher than samariadoped ceria (SDC) ionic conductivity [8]. BSCF reacts with CO 2 present in air, forming oxides and carbonates [9,10]. The TEC of BSCF is much larger than TEC of LSCF [6,7].…”