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_0.44Ce_0.36Y_0.2O_3−δ protonic half-cells with impressive dimensions of up to 50 mm × 50 mm. The cells are constructed using NiO-SrZr_0.5Ce_0.4Y_0.1O_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 dm³ s⁻¹ cm²)⁻¹. Using B_0.5La_0.5CoO_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.