Alkaline Leaching: A Facile Surface Activation Strategy to Improve the Reactivity of Air Electrodes for Solid Oxide Fuel Cells

The energy conversion efficiency of solid oxide fuel cells is primarily governed by the performance of their air electrodes. Several surface modification techniques, including nanocatalyst decoration, surface coating, and acid etching, have been reported to enhance the performance of air electrodes. However, these approaches often face limitations in cost and time efficiency. In this study, we propose alkaline leaching as a straightforward and innovative strategy to activate the surface of mixed-conducting oxides by selectively dissolving the A-site cation during bias application in an alkaline solution. After 10 min of alkaline leaching, the surface of the PrBa_0.8Ca_0.2Co₂O_5+δ electrode becomes cobalt-rich and amorphous, recognized for its favorable impact on reactivity. As a result, when the surface-modified electrode is used as the air electrode in a solid oxide fuel cell, it exhibits a 5.6 fold enhancement in catalytic activity, achieving an area-specific resistance of 0.019 Ω cm². Single cell measurements further demonstrate a 33 % increase in maximum power density, reaching 2.10 W cm^-2 at 650°C. This work provides a strategic approach for engineering highly active oxide surfaces, leveraging a straightforward system operable at ambient pressure and room temperature, with broad applicability across diverse devices.