Performance of Plasma-Sprayed Bi₂O₃–Er₂O₃–WO₃ for Intermediate-Temperature Solid Oxide Fuel Cells (IT-SOFCs)

The previous results have shown that dense bismuth oxidebased electrolytes can be fabricated simply by plasma spraying owing to their low melting point. In this study, the Bi₂O₃– Er₂O₃–WO₃ electrolyte of high ionic conductivity was deposited by the cost-effective plasma spraying to assemble the SOFC for examining its electrochemical performance. The SOFC cell consisted of FeCr_24.5 metal support, NiO-YSZ anode, 10 mol% scandium oxide-stabilized zirconium oxide (ScSZ) electrolyte, (Bi₂O₃)_0.705 (Er₂O₃)_0.245 (WO₃)_0.05 (EWSB) electrolyte, and La_0.6Sr_0.4Co_0.2Fe_0.8O₃ (LSCF) cathode. The ScSZ electrolyte interlayer was introduced between the anode and EWSB electrolyte to hinder the reduction of EWSB in the anode environment. NiO-YSZ, ScSZ, EWSB, and LSCF were deposited by plasma spraying on the metal support which was prepared by a press-forming-sintering process. The NiO-YSZ/ ScSZ/ EWSB/ LSCF single cell assembled with the as-sprayed ScSZ presented an open circuit potential of 0.90V at 600 °C and the maximum power density of 1130 mW cm^-2 at 750 °C, 450 mW cm^-2 at 650 °C, and 128 mW cm^-2 at 550 °C. The plasma sprayed ScSZ electrolyte was then densified through impregnating using yttrium and zirconium nitrate solutions followed by annealing treatment. The single cell assembled with the densified ScSZ presented an open circuit potential up to 1.004V at 600 °C and the maximum power density of 1356 mW cm^-2 at 750 °C, 619 mW cm^-2 at 650 °C, and 163 mW cm^-2 at 550 °C. The performance of the cell was significantly improved by the post-spray densification treatment of the ScSZ electrolyte. The present result shows that the high performance NiO-YSZ/ScSZ/EWSB/LSCF cell at intermediate temperatures can be successfully fabricated by plasma spraying.