New SOFC Cathode: 3D Core–Shell-Structured La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ@PrO_2−δ Nanofibers Prepared by Coaxial Electrospinning

3D core–shell La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF)@PrO2−δ nanofibers as a solid-oxide fuel cell (SOFC) cathode with excellent electrochemical properties are directly prepared by coaxial electrospinning. In the LSCF@PrO2−δ nanofibers, the low oxygen reduction reaction (ORR) activity of LSCF can be effectively ameliorated by heterogeneous PrO2−δ. Compared with the LSCF nanostructure, the LSCF@PrO2−δ nanofibers with a 3D core–shell heterostructure effectively suppress the segregation of Sr on the surface and improve the stability of the cathode. Due to the unique microstructure, large specific surface area, and porosity, the LSCF@PrO2−δ nanofibers provide a continuous path for charge transfer and extend the three-phase interface that help to improve the ORR activity of the SOFC cathode. At 700 °C, the area specific resistance of LSCF@PrO2−δ nanofibers reaches 0.076 Ω·cm2, which is reduced by 35 and 60%, compared with 0.117 Ω·cm2 of LSCF nanofibers and 0.192 Ω·cm2 of the LSCF powder. When LSCF@PrO2−δ nanofibers are used as a single-cell cathode, the peak power density reaches 1.17 W·cm–2 at 700 °C, and the voltage decay rate of the single cell is only 0.03% per hour after 100 h of long-term stability test. Therefore, the 3D core–shell LSCF@PrO2−δ nanofibers provide an alternative approach for obtaining the high-performance SOFC cathode.