Interface-driven boost in the performance and stability of protonic ceramic electrochemical cells

Interfacial resistance remains a key challenge in developing high-performance and durable protonic ceramic electrochemical cells (PCECs), especially at low temperatures. Here, we present a systematic interface engineering strategy that quantitatively correlates interfacial contact coverage with electrochemical performance. A thin and dense PrBa_0.5Sr_0.5Co_1.5Fe_0.5O_5+δ interlayer is fabricated via low-cost and scalable precursor-based electrostatic spray deposition on a BaZr_0.4Ce_0.4Y_0.1Yb_0.1O_3-δ electrolyte, achieving a nearly complete contact coverage of 92.6 ± 0.6%. Equivalent circuit-based impedance modeling confirms that the improved contact coverage reduced both the interfacial ohmic and polarization resistances. The interface-engineered PCEC achieves a peak power density of 1.01 W/cm² in fuel cell mode and a current density of 1.15 A/cm² at 1.3 V in electrolysis mode at 500 °C. It also demonstrates improved interfacial mechanical integrity, preventing delamination under harsh thermal cycling, long-term operational stability, and fuel flexibility with direct ammonia and methane.