Tailoring the Reversible Phase Transition of Perovskite Nanofiber Electrodes for High-Performance and Durable Reversible Solid Oxide Cells

• LSTCF nanofibers with in situ exsolved Co3Fe7 nanoparticles exhibit high structural reversibility and enhanced electrochemical performance. • The reversible phase transition between perovskite and exsolved nanoparticles enables superior activity and stability in both fuel cell and electrolysis modes. • The symmetrical electrode achieves high power densities (0.98 W cm−2 with H2, 0.53 W cm−2 with CH4) and high current densities for CO2 and H2O electrolysis at 800 °C. • The electrode demonstrates excellent durability over 100 hours, highlighting its potential for practical RSOC applications.