Valence regulation of ferrite perovskite for high performance cobalt-free cathode of solid oxide fuel cell

Summary The development of a cobalt-free cathode with long-term stability and high electrochemical activity is important for constructing low-cost and robust solid oxide fuel cells (SOFCs). Here, we report performance enhancement of a cobalt-free cathode achieved by valence regulation of the ferrite-based perovskite. Utilizing co-doping of high valence niobium with low valence nickel, we developed a cathode material La 0.8 Sr 0.2 Fe 0.8 Ni 0.15 Nb 0.05 O 3−δ that allowed representing adequate conductivity of 214 S cm −1 at 700°C, decent thermal compatibility with thermal expansion coefficient being 12 × 10 −6 K −1 , superior electrochemical properties manifested by area-specific resistance of 0.06 Ω cm 2 and peak power density of 760 mW cm −2 at 800°C, and excellent discharge durability of over 480 h at a current density of 460 mA cm −2 under 750°C. This significantly enhanced performance originates from a proper regulation of the electronic structure rendered by synergistic effects induced by the co-doping of the high valence niobium with low valence nickel into the B sites of the ferrite perovskite. Such a regulation enables an optimized compromise among the oxygen vacancies, electronic mobility, oxygen adsorption and dissociation, and strontium segregation.