Improving the Activity and Stability of La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ Cathode Through Surface Modification with an...

Although the conventional commercial solid oxide fuel cells cathode La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF) exhibits excellent electrochemical performance, its oxygen reduction reaction (ORR) kinetics are still sluggish, and Strontium (Sr) segregation is also an issue for long-term stability. Herein, a Sr-free electro-catalyst PrBa_0.9Cs_0.1Co₂O_5+δ (PBCsC) is infiltrated on the surface of LSCF to form a PBCsC-LSCF electrode, accelerating the surface oxygen exchange and thus improving the ORR activity and stability. PBCsC-LSCF shows a higher concentration of oxygen vacancies and less Sr segregation, as confirmed by the analyses of X-ray photoelectron spectroscopy (XPS). As a result, PBCsC-LSCF demonstrates an area-specific resistance of 0.010 Ω cm² at 750 °C, much lower than 0.067 Ω cm² of a bare LSCF. An improved peak power density of 1.70 W cm^-2 is reached from the single cell with PBCsC-LSCF at 750 °C, likely due to the higher oxygen surface exchange, as indicated by the distribution of relaxation time analyses. In addition, the cells' operational stability is greatly improved at a current density of 0.5 A cm^-2 with a degradation rate of 0.055% h^-1, probably attributable to the suppression of Sr segregation by infiltration, as suggested by the XPS results.