Dual-Donor Doped Perovskite as Bifunctional Oxygen Electrode Catalyst for Reversible Protonic Ceramic Electrochemical Cell

Developing high-performance bifunctional oxygen electrodes is crucial for advancing the reversible protonic ceramic electrochemical cell (R-PCEC). Here, we report a novel Nb-Ta codoped BaCoO3-δ perovskite oxygen electrode that exhibits enhanced bifunctional catalytic activity, enabled by modulation of metal-oxygen bonding. Dual-donor doping with Nb and Ta suppresses Co-O hybridization, thereby weakening Co-O bonds and promoting both oxygen activation and vacancy formation. The increased oxygen vacancy concentration, coupled with reduced hydration energy and a proton hopping barrier, synergistically enhances proton hydration and migration. Consequently, the R-PCEC with the BaCo0.8Nb0.1Ta0.1O3-δ oxygen electrode achieves remarkable performance, with a peak power density of 1.20 W cm⁻² in fuel cell mode and a current density of 1.32 A cm⁻² at 1.3 V in electrolysis cell mode at 650 °C. This work elucidates the underlying mechanism by which dual-donor doping modulates defect chemistry and transport properties in perovskite catalysts, offering a rational design strategy for efficient oxygen electrodes in R-PCEC and broader energy conversion technologies.