In-situ surface reconstruction induced-significant performance promotion of Ca₃Co₄O_9+δ cathode for solid oxide fuel cells

Surface morphology of cathode has a significant impact on the oxygen reduction reaction (ORR) activity as well as the performance of solid oxide fuel cells (SOFCs). Up to now, great efforts have been devoted to decorate the microstructure of SOFC cathode, such as changing synthesis method, infiltration, electrospinning and so on. Herein, we report an effective and feasible method to reconstruct the surface of Ca₃Co₄O_9+δ (CCO) cathode by reduction and re-oxidation process, during which remarkable morphology change is observed as the surface is wrinkled with the formation of numerous small particles. ORR activity of CCO cathode is notably improved after surface reconstruction, since area specific resistance (ASR) of CCO cathode significantly decreases from 0.48 Ωcm² to 0.19 Ωcm² at 700 °C. Specific surface area of CCO increased and calcium and cobalt oxide nanoparticles are generated after the redox treatment. The oxygen adsorption ability of the CCO is largely enhanced, which contributes to the performance promotion of CCO cathode after the redox treatment. Overall, we propose a feasible method to reconstruct CCO surface to promote the ORR activity effectively and study the corresponding mechanism thoroughly, all of which make valuable improvements on the development of SOFC cathode.