Robust tantalum tuned perovskite oxygen electrode for reversible protonic ceramic electrochemical cells

Perovskite oxides with diverse composition and structure have exhibited grand advances in boosting the oxygen reduction and evolution reaction (ORR/OER), which are essential for the reversible protonic ceramic electrochemical cell (R-PCEC) toward the sustainable hydrogen production and utilization. However, enhancement of their activity and stability remains challenging. Herein, we develop the Ta-regulated BaCo_0.7Fe_0.3O_3−δ perovskite oxygen electrode (Ba(Co_0.7Fe_0.3)_1−xTa_xO_3−δ) with abundant oxygen defects and achieve the simultaneous enhancement in the electrocatalytic activity and stability toward ORR and OER. As-fabricated R-PCEC with Ba(Co_0.7Fe_0.3)_0.9Ta_0.1O_3−δ (BCFT10) oxygen electrode performs high power density of 1.47 W·cm⁻² at 650 °C in fuel cell mode, and the current density is up to − 2.11 A·cm⁻² at 1.4 V at 650 °C in electrolysis mode, as well as the good stability in both the fuel cell and electrolysis modes. Importantly, the cell also demonstrates a stable cycling operation between fuel cell and electrolysis mode, suggesting a great potential of BCFT10 as oxygen electrode material for R-PCECs.