Efficient perovskite cathode for solid oxide fuel cells towards enhanced oxygen reduction activity and stability by water-mediated exsolution

Highly efficient and stable cathodes are significantly vital for solid oxide fuel cells (SOFCs). However, one of key impediment to the cathode development is the undesirable oxygen reduction activity and stability with exposure upon steam. Herein, we present a novel nanoparticles-decorated cathode, comprised of O2 -/e -/H+ triple -conducting K+-doped BaCo0.7Fe0.2Y0.1O3-delta (Ba0.9K0.1Co0.7Fe0.2Y0.1O3-delta, BKCFY) matrix oxide and the mixed O2 -/e- conducting nanoparticles of BaCoO3-delta (BCO) through water-mediated exsolution process, exhibiting high activity and robust stability with exposure upon the steam. The cathode shows a low polarization resistance of 0.048 omega cm2 at 700 degrees C when exposed upon humid air with 3% H2O, approximately 24% lower than that in dry air (0.065 omega cm2 at 700 degrees C). Such improvement is mainly ascribed to the exsolved BaCoO3-delta nanoparticles decorated on the porous BKCFY, which enlarged the triple phase boundary for oxygen reduction reaction. The increased oxygen vacancy concentration through K doping can accelerate the Ba and Co ions segregation to form BaCoO3-delta with exposure upon the wet condition. Furthermore, K+ dopant with higher basicity than Ba2+ is beneficial for hydration behavior, which effectively promotes the catalytic activity under the water vapor. Moreover, the exsolved BaCoO3-delta nanoparticles are socketed on the BKCFY matrix oxide, which ensures high stability for this hybrid cathode operated at 700 degrees C. The findings provide a promising approach to design the triple-conducting cathode for solid oxide fuel cells via water-mediated exsolution, which can also be applied for solid oxide electrolysis cells and membrane reactors.

Automated summary

A novel nanoparticles-decorated cathode comprised of K+-doped BaCo0.7Fe0.2Y0.1O3-delta matrix oxide and the mixed BaCoO3-delta nanoparticles through water-mediated exsolution process showed high activity and stability upon exposure to steam. The improved performance was attributed to the enlarged triple phase boundary and increased oxygen vacancy concentration. The cathode also benefitted from the hydration behavior of K+ dopant and the stability provided by the socketed nanoparticles.