The emerging applications of steam electrolysis and electrochemical synthesis at 300-600 oC 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 (BZY), yet its usage has long been denied due to sinterability conundrum in protonic devices. Here we resolved the issue by a renovated co-sintering process, in which the shrinkage stress of a readily sinterable support layer helps densify pure BZY electrolyte membrane at record low temperatures. It eliminates Ce and harmful sintering aids in zirconate cells and enhances Faraday efficiency and electrochemical stability, especially under harsh operation 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 hours of dynamic operation at 600 oC. Our processing breakthrough enables stabilized protonic cells in demanding applications in future energy infrastructure.

This work was completed by multiple institutions including Idaho National Laboratory, New Mexico State, OU, Georgia Tech, Tsinghua University, and MIT.

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