Microwave plasma rapid heating towards robust cathode/electrolyte interface for solid oxide fuel cells

Mixed electronic and ionic conductivity (MIEC) perovskite oxides hold promise as cathode with high oxygen reduction reaction (ORR) activity for solid oxide fuel cells (SOFCs) operating at reduced temperatures. However, these MIEC cathodes usually contain lanthanide or alkaline-earth elements at A-site. These elements tend to interact with yttria-stabilized zirconia electrolyte (YSZ) to form unwanted phases such as La₂Zr₂O₇ and SrZrO₃ at conventional electrode fabrication conditions (>800 °C). Such unwanted interfacial reaction severely degrades the cell performance. We present a new method to assemble SrCo_0.4Fe_0.5W_0.1O_3-δ (SCFW) directly onto YSZ by a highly efficient microwave plasma technique. Intimate contact between SCFW and YSZ phases can be achieved by ten-minute microwave-plasma treatment with no new phase formation. Consequently, the microwave-plasma fabricated interface exhibits a notably high ORR performance, showing an area-specific resistances of 0.11 Ω cm² at 600 °C, about two orders of magnitude better than the equivalent prepared via the conventional method. Our method is also effective in assembling other MIEC perovskite cathodes such as SrCo_0.5Fe_0.5O_3-δ and SrCo_0.8Nb_0.1Ta_0.1O_3-δ on YSZ electrolyte, achieving notable enhancement of the cathode performance. This study thus provides an effective and convenient method for synthesizing reactive and robust interfaces between two incompatible phases with minimized interphase interactions.