An In Situ Formed, Dual‐Phase Cathode with a Highly Active Catalyst Coating for Protonic Ceramic Fuel Cells

Composite cathodes of solid oxide fuel cells (SOFCs) are normally fabricated by mechanical mixing of electronic‐ and ionic‐conducting phases. Here, a dual‐phase SOFC cathode, composed of perovskite PrNi0.5Mn0.5O3 (PNM) and exsoluted fluorite PrOx particles, produced in situ through a glycine–nitrate solution combustion process, is reported. When applied as the cathode for a BaZr0.1Ce0.7Y0.1Yb0.1O3‐based protonic ceramic fuel cell, the hybrid cathode displays excellent electrocatalytic activity (area‐specific resistance of 0.052 Ω cm2 at 700 °C) and remarkable long‐term stability when operated at a cell voltage of 0.7 V for ≈500 h using H2 as fuel and ambient air as oxidant. The excellent performance is attributed to the proton‐conducting BaPrO3‐based coating and high‐concentration oxygen vacancies of a Ba‐doped PNM surface coating, produced by the reaction between the cathode and Ba from the electrolyte (via evaporation or diffusion), as confirmed by detailed X‐ray photoelectron spectroscopy, Raman spectroscopy, and density functional theory‐based calculations. A high‐performing dual‐phase electrode for protonic ceramic fuel cells is developed. An oxygen‐vacancy‐rich surface coating and a proton‐conducting coating, derived from a reaction between the electrode and Ba from the electrolyte, significantly enhance the rate of the oxygen reduction reaction.