Efficient intermediate-temperature steam electrolysis with Y:SrZrO₃-SrCeO₃ and Y:BaZrO₃-BaCeO₃ proton conducting perovskites

Ceramic proton conductors have the potential to become important components in future clean and efficient energy technologies. In this manuscript, barium cerium yttrium zirconate (Ba(Zr_0.5Ce_0.4)_8/9Y_0.2O_2.9) and strontium cerium yttrium zirconate (SrZr_0.5Ce_0.4Y_0.1O_2.95), proton conducting perovskites were employed as solid oxide electrolysis cell (SOEC) electrolytes for hydrogen production via intermediate temperature steam electrolysis at 550 and 600 °C. Cathode-supported button cells examined for a 12 μm Ba(Zr_0.5Ce_0.4)_8/9Y_0.2O_2.9 electrolyte, with Ni-SrZr_0.5Ce_0.4Y_0.1O_2.95 as the H₂-electrode, and porous Ba_0.5La_0.5CoO₃ as the anode reached current densities of 0.2 and 0.5 A cm^-2 with applied voltage of 1.45 V, at 550 and 600 °C, respectively. Moreover, a hydrogen evolution rate of 127 μmol cm^-2 per minute was achieved at 0.5 A cm^-2, translating to a current efficiency of 82%. In addition, excellent cell performance was obtained using SrZr_0.5Ce_0.4Y_0.1O_2.95 as an electrolyte. Current densities of 0.2 and 0.5 A cm^-2 were obtained at 600 °C with applied voltages of 1.28 and 1.63 V, achieving faradaic current efficiencies of 88 and 85%. The NiO-SrZr_0.5Ce_0.4Y_0.1O_3-δ composite cathode was more favorable for the densification of the supported Ba(Zr_0.5Ce_0.4)_8/9Y_0.2O_2.9 electrolyte during sintering and could be promising for use as a cathode substrate in proton-conducting SOECs.