Hybrid-Scale Powder Engineering Enables High-Performance, Durable, and Scalable Protonic Ceramic Electrochemical...

Protonic ceramic electrochemical cells (PCCs) offer an efficient pathway for electricity-hydrogen interconversion at intermediate temperatures, yet their practical deployment is hindered by complex fabrication routes and limited scalability. Here, we report a powder-to-cell engineering strategy that directly links electrolyte precursor design to cell-level performance. A hybrid-scale BaCe_0.7Zr_0.1Y_0.1Yb_0.1O_3-δ (BCZYYb) precursor, integrating microscale BaCO₃ with nanoscale metal oxides, enables reaction-assisted sintering that improves electrolyte densification, suppresses cation segregation, and promotes proton transport. Cells fabricated from this hybrid-scale powder deliver ∼60% higher power densities than those prepared from fully nanoscale precursors. Importantly, the hybrid-scale powder can be synthesized at the kilogram scale and is compatible with cost-effective ceramic processing, enabling the fabrication of large-area single cells via tape casting, lamination, and co-sintering. These scaled-up PCCs exhibit high electrochemical performance and stable steam electrolysis operation at current densities up to 1 A cm^{- 2}, with a low degradation rate of 0.8% kh^{- 1}.