Sintering protonic zirconate cells with enhanced electrolysis stability and Faradaic efficiency

The emerging applications of steam electrolysis and electrochemical synthesis at 300–600 °C set stringent requirements on the stability of protonic ceramic cells, which cannot be met by Ce-rich electrolytes. A promising candidate is Ce-free BaZr0.8Y0.2O3−δ, but its usage has long been hindered due to the high sintering temperatures required for protonic devices. Here we resolved the issue through a co-sintering process, in which the shrinkage stress of a readily sinterable support layer helps to densify the pure BaZr0.8Y0.2O3–δ electrolyte membrane at low temperatures. This approach eliminates Ce and harmful sintering aids in the dense zirconate electrolyte membrane, thereby enhancing the Faradaic efficiency and electrochemical stability, especially under harsh operating conditions. The protonic zirconate cells have exceptional performance and demonstrate stable high-steam pressure electrolysis up to 0.7 atm steam pressure, −2 A cm−2 current density and over 800 h of dynamic operation at 600 °C. Our processing breakthrough enables stabilized protonic cells for demanding applications in future energy infrastructure. Emerging applications of steam electrolysis and electrochemical synthesis for future hydrogen technologies at intermediate temperatures set stringent requirements on the stability of protonic ceramic cells. Now a sintering approach enables densified Ce-free protonic zirconate cells with enhanced Faradaic efficiency and exceptional stability under harsh operating conditions.