Unlocking refractory BaZrO 3 -based protonic ceramics via cooperative interfacial low-temperature processing for electrochemical cells

Refractory BaZrO3-based protonic ceramics offer outstanding chemical stability for protonic ceramic electrochemical cells but require sintering temperatures exceeding 1550 °C because of sluggish cation diffusion, leading to detrimental Ba volatilization, electrode coarsening, and microstructural degradation. Here, we report low-temperature processing of BaZr0.8Y0.2O3-δ (BZY) at only 1350 °C though a cooperative interfacial co-sintering strategy enabled by defect-structure coupling across the electrolyte/support interface. Zinc incorporation increases oxygen-vacancy concentration and is accompanied by enhanced sintering kinetics within the BZY electrolyte, while a Ni-modified BCZYYb support promotes cooperative membrane densification. Electron paramagnetic resonance and X-ray photoelectron spectroscopy confirm enhanced oxygen-vacancy formation, while the reduced thermal budget suppresses Ba evaporation and Ni coarsening, producing a fully dense electrolyte with a proton conductivity of ~0.01 S cm-1 at 550 °C. The resulting cells deliver reversible electrochemical operation with electrolysis current densities reaching -4 A cm-2 at 1.5 V and exceptional durability, exhibiting an ohmic degradation rate of only 0.012% h-1. This work establishes a defect-chemistry-guided, scalable processing strategy for overcoming diffusion-limited sintering in refractory protonic ceramics and provides a broadly applicable route toward low-temperature manufacturing of advanced solid-state electrochemical devices.