Synergistic oxygen vacancy-hydration regulation in perovskite oxide for high-performance protonic ceramic electrolysis cell oxygen electrode

The proton ceramic electrochemical cell (PCEC), distinguished by its robust all-solid-state construction, emerges as a particularly promising contender in the realm of hydrogen production technologies. However, inadequate water-storage capability (hydration) and limited proton mobility within conventional PCEC oxygen electrodes hinder the efficiency of water splitting to oxygen, thereby restricting the broader application of PCECs. Here, we report a Ni-doped perovskite oxygen electrode Sr₂Fe_1.4Ni_0.1Mo_0.5O_6-δ (SFNM), where the incorporation of nickel can effectively amplify the concentration of oxygen vacancies while synergistically enhancing the hydration interaction between water molecules and the perovskite lattice. The enhanced hydration capacity facilitates proton-defect formation and lowers the energy barrier for proton migration. Benefiting from these synergistic enhancements, SFNM demonstrates a substantially reduced polarization resistance of approximately 0.078 Ω cm² at 700 °C under humidified conditions (pH₂O = 0.1 atm). A PCEC utilizing the SFNM electrode achieves a remarkable current density of 2.60 A cm² with an applied voltage of 1.3 V at 700 °C. Furthermore, the PCEC exhibits favorable stability over a duration of 200 h. These outstanding results emphasize the potential of Ni doping to substantially improve both the hydration efficiency and proton mobility within perovskite electrode materials, positioning them as excellent candidates for high-performance PCECs.