A dynamic infiltration technique to synthesize nanolayered cathodes for high performance and robust solid oxide fuel cells

Abstract

Solution infiltration is a popular technique for the surface modification of solid oxide fuel cell (SOFC) cathodes. However, the synthesis of nanostructured SOFC cathodes by infiltration is a tedious process that often requires several infiltration and high temperature (≥500 °C) calcination cycles. Moreover, fabricating large-area nanostructured cathodes via infiltration still requires serious attention. Here, we propose a facile and scalable urea assisted ultrasonic spray infiltration technique for nanofabrication of SOFC cathodes. It is demonstrated that by using urea as a precipitating agent, the calcination after each infiltration cycle can be omitted and the next infiltration can be performed just after a drying step (≤100 °C). Finally, the precipitates can be converted into a desired catalyst phase in single calcination thus, a nanostructured cathode can be fabricated in a much faster manner. It is also shown that the low calcination temperature of the cathode (≤900 °C) can produce highly durable SOFC performance even without employing a Ce0.9Gd0.1O2 (GDC) diffusion barrier layer which provides the ease of SOFC fabrication. While coupling with an ultrasonic spray technique, the urea assisted infiltration can be scaled up for any desired cathode area. La0.6Sr0.4Co0.2Fe0.8O3 nanolayered cathode was fabricated and it was characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM) techniques. SEM showed the formation of a nanolayer cathode just after 5 cycles of the urea assisted infiltration while the XRD and TEM confirmed the phase and stoichiometric uniformity of the ∼100 nm cathode nanolayer. The effectiveness of the newly developed technique was further verified by the stable operation of a GDC buffer layer free SOFC having an active cathode area of 25 cm2 during a 1200 h durability test. The research outcomes propose urea assisted ultrasonic spray infiltration as a facile, scalable, and commercially viable method for the fabrication of durable nanostructured SOFC cathodes.