Optimization of misfit calcium cobaltite oxygen electrodes for solid oxide fuel cells through electrospinning processing

Abstract

Current research in oxygen electrodes for Solid Oxide Fuel Cell applications underscores that the commercialization process of this technology remains severely limited by the poor oxygen reduction reaction performance of cathode materials. The misfit calcium cobalt oxide [Ca₂CoO_3−δ]_0.62[CoO₂] (CCO) presents a promising prospect in this regard, boasting fast surface-exchange kinetics coupled to a thermal expansion coefficient closely aligned with that of standard electrolytes. Nevertheless, its polarization losses are limited by a poor bulk oxygen-ion conduction, which confines the oxygen diffusion to a surface pathway, where the microstructure plays a significant role. Therefore, this study explores an alternative processing route for the synthesis of CCO via the electrospinning technique, resulting in a microstructure composed of small platelet-like grains with increased surface area, as well as enhanced grain-to-grain connectivity. Our work comprehensively assesses the particular benefits of electrospinning, where both the fiber breakage during the electrode preparation and the higher aspect ratio of the synthesized particles play a key role in the final electrode microstructure. This modification significantly enhances the electrochemical processes of the CCO electrode prepared by this route, resulting in a reduction of the total polarization resistance between 60% and 69% in the temperature range (800 to 600) °C, compared to a sample produced by the state-of-the-art solid-state reaction. Overall, our work highlights electrospinning as a promising alternative methodology for fabricating CCO cathodes with superior electrochemical performance.