Spontaneous Growth of Perovskite‐Derived Oxide over Double Perovskite Surface for Enhancing Cathodic Performance in Protonic Ceramic Fuel Cells

Abstract Robust catalytic materials with high activity and stability play important roles in energy conversion and storage devices such as protonic ceramic fuel cells (PCFCs), in which a favourable cathode should possess high oxygen ion, proton and electron triple conductivities, and superior surface oxygen exchange kinetics. Herein, a thermal‐driven self‐construction phenomenon in cation‐nonstoichiometric Ba 1+x Gd 1‐x Co 2 O 6‐δ is reported, accordingly developing a new type of nanocomposite, that is, double perovskite BaGdCo 2 O 6‐δ (DP‐BGCO) anchored by perovskite‐derived BaCoO 3‐δ (P‐D‐BCO) nanoparticles, which, used as the cathode of PCFCs, demonstrates low area‐specific resistances of 0.053 and 0.026 ohm cm −2 respectively at 650 and 700 °C over BaZr 0.3 Ce 0.5 Y 0.1 Yb 0.1 O 3‐δ protonic electrolyte and attractive peak power densities of 0.87 (650 °C) and 1.15 W cm −2 (700 °C) with outstanding stability, much superior to the similar cell with single‐phase BCO or BGCO cathodes. The synergy between the two components brings the outstanding performance with the mixed oxygen ion and electronic conducting perovskite‐derived oxide showing superior catalytic activity for oxygen reduction reaction while the double perovskite provides good bulk protonic conductivity to enlarge reaction sites. Such selective self‐construction, well manipulated through the A‐site cation stoichiometry engineering, provides a facile way for developing new high‐performance electrocatalysts with broad application potential.