Toward highly efficient protonic electrolysis cells for large-scale hydrogen production at moderate temperatures

Ceramic proton-conducting electrolytes are highly appealing for large-scale hydrogen production via steam electrolysis at low to moderate temperatures. However, processing such electrolytes for industrial purposes poses several challenges. Our research demonstrates an effective tape-casting route that produces flat, planar BaZr_<0.44>Ce_<0.36>Y_<0.2>O_<3−δ> protonic half-cells with impressive dimensions of up to 50 mm × 50 mm. The cells are constructed using NiO-SrZr_<0.5>Ce_<0.4>Y_<0.1>O_<3−δ> as the fuel electrode, which ensures minimal warping and no cracks in the end-fired state. The electrolyte is dense and gas-tight after co-firing at 1300 °C and achieves a He leakage rate well within the threshold necessary for cell operation (∼5 × 10^<−5> hPa dm^3 s^<−1> cm^2)^<−1>. Using B_<0.5>La_<0.5>CoO_<3−δ> as the steam electrode, the cell achieves an electrolysis voltage of 1.3 V at a current density of 1.37 A cm^<−2> at 600 °C. Moreover, they also exhibit high durability, lasting over 1000 hours of continuous hydrogen generation with no observable degradation, which is a testament to their reliability. In addition, scanning electron microscopy paired with energy-dispersive X-ray spectroscopy, Raman spectroscopy, and X-ray diffraction were employed to examine the structural changes in the half-cells after sintering at different temperatures. It is apparent from the latter techniques that upon sintering above 1350 °C, the electrolyte undergoes evident structural changes with new defects that affect the perovskite host. Finally, our work paves the way for the cost-effective fabrication of planar proton-conducting electrolysis cells.