Enhancing\nElectrochemical Performance of Reversible\nSolid Oxide Cells with Double Element-Deficient Pr<sub>0.97</sub>Ba<sub>0.97</sub>Co<sub>1.5</sub>Fe<sub>0.5</sub>O<sub>5+δ</sub> Oxygen

Reversible solid oxide cells (RSOCs) are state-of-the-art\nall-solid-state\nenergy conversion devices that operate as either solid oxide fuel\ncells (SOFCs) or solid oxide electrolysis cells (SOECs), with the\noxygen electrode playing a critical role in both the oxygen reduction\n(ORR) and oxygen evolution (OER) reactions. Herein, PrBaCo<sub>1.5</sub>Fe<sub>0.5</sub>O<sub>5+δ</sub> (PBCF) is modified via double\ndeficiency modulation of the A-site to improve its performance as\nan RSOC oxygen electrode. The cation-deficient variant, Pr<sub>0.97</sub>Ba<sub>0.97</sub>Co<sub>1.5</sub>Fe<sub>0.5</sub>O<sub>5+δ</sub> (PBCF97), exhibits a balanced oxygen vacancy concentration and ionic\nconductivity. RSOCs using PBCF97-Gd<sub>0.1</sub>Ce<sub>0.9</sub>O<sub>2</sub>(GDC) as the oxygen electrode achieve a peak power density\nof 1.685 W/cm<sup>2</sup> in SOFC mode and a current density of 2.61\nA/cm<sup>2</sup> at an electrolytic voltage of 1.5 V in SOEC mode\nat 800 °C. In addition, the cell demonstrates stable reversible\noperation for 160 h, highlighting its potential for advanced RSOC\napplications.