Chlorine doped K2NiF4-type oxide as an efficient oxygen reduction catalyst for protonic ceramic fuel cells

Protonic ceramic fuel cells (PCFCs) operated at medium temperatures have attracted plenty of researches due to their many advantages, such as high efficiency for energy conversion, easier sealing, catabatic material aging, no attenuation of fuel and so on. However, the industrial application of PCFCs is greatly fettered by the development of high-performance cathodes with superior oxygen reduction reaction (ORR) kinetics. In this work, a chlorine doped K 2 NiF 4 -type oxide named as Pr 1.8 La 0.2 Ni 0.74 Cu 0.21 Ga 0.05 O 4+ δ Cl 0.1 (PLNCGCl 0.1 ) is developed as the cathode for PCFC according to the BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3− δ (BZCYYb) electrolyte, which demonstrates enhanced ORR kinetics, as corroborated by a series of structural analysis and electrochemical characterizations. Theoretical simulations have shown that doping Cl not only favors interstitial oxygen formation thermodynamically, but also alleviates the kinetic energy hurdle associated with the oxygen reduction reaction’s critical rate-determining step. An anode-supported PCFC with PLNCGCl 0.1 as the cathode outputs peak power density (PPD) of 1.162 W cm −2 and the polarization resistance (R p ) is 0.069 Ω cm 2 at 700 °C. This work paves an efficient venue for the development of active and durable K 2 NiF 4 -type cathode by Cl-doping with high ORR kinetics.