Redox-reversible perovskite ferrite cathode for high temperature solid oxide steam electrolyser

In this work, perovskite Sr1−xPrxFeO3-δ (SPF) (x = 0.02, 0.04, 0.06, 0.08 and 0.10) are investigated and employed as solid oxide steam electrolyser cathode at 800 °C. X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscopy (TEM) analysis together indicate that the Sr1−xPrxFeO3-δ is redox reversible with a phase transition from cubic to orthorhombic structure in redox cycles. The doping of Pr in A site has remarkably enhanced the electronic conduction to 1.0-1.2 S cm−1 at intermediate temperatures in reducing atmosphere. Electrochemical measurements demonstrate that the polarization resistance with Sr0.96Pr0.04FeO3-δ electrode shows the lowest values of 0.25 Ω cm2 in symmetric cells in reducing atmosphere at 800 °C. Direct steam electrolysis with Sr0.96Pr0.04FeO3-δ cathode shows a current density of 1.64 A cm−2 at 2.0 V when fed with 5%H2O/Ar. The hydrogen production rate reaches 4.73, 6.68, 8.35 and 10.23 mL min−1 cm−2 at 1.4, 1.6, 1.8, 2.0 V, respectively, while the highest Faraday efficiency is as high as 97.16% at 1.8 V.