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 La0.8Sr0.2Fe0.8Ni0.15Nb0.05O3−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 cm2 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. LSFNNb cathode with high performance and good stability was developed for SOFCs using valence regulation strategy.