Advancing proton-conducting ceramic cells with thin electrolyte layers prepared by wet powder spraying

• A 3 μm proton-conducting electrolyte was made via wet powder spraying. • Thin electrolyte enables proton transport without grain boundary obstruct. • Dense electrolyte layer achieved at 1375 °C on SrZr 0.5 Ce 0.4 Y 0.1 O 3 -based substrate. • 422 mW/cm 2 power density reached at 600 °C, 0.7 V in fuel cell mode. The development of proton conducting high temperature solid state electrochemical cells (PCCs) is vital for energy conversion and storage. Here, a SrZr 0.5 Ce 0.4 Y 0.1 O 3-δ (SZCY) / NiO supported cell with a 3 μm BaZr 0.16 Ce 0.64 Y 0.1 Yb 0.1 O 3-δ electrolyte, deposited by wet powder spraying (WPS), was fabricated. Co-sintering at 1375 °C yielded a dense electrolyte layer with large grains. Sr diffusion from the SZCY substrate compensated for Ba evaporation, preventing the formation of Y-rich secondary phases and thereby enhancing sinterability. STEM confirmed elemental diffusion and verified the proton transport without grain boundary obstruct in the thin electrolyte layer. The fabricated PCC achieved 422 mW cm −2 at 0.7 V and 600 °C in fuel cell mode, demonstrating competitive electrochemical performance. Minor defects in the electrolyte layer contributed to reduced open-circuit voltage (OCV) at lower temperatures, attributed to contamination during substrate pre-treatment. This work demonstrates the viability of WPS for scalable fabrication of thin PCC electrolyte layers with enhanced electrochemical performance.