Highly ionic-dispersed oxygen electrode for reversible proton ceramic electrochemical cells

The key challenges for commercializing reversible proton ceramic electrochemical cells (R-PCECs) are the insufficient proton conductivity and inferior thermomechanical stability of oxygen electrodes in air with water vapor. We report a multielement micro-doped BaCoO_3-δ-based perovskite material, in which disorder is induced in the ionic substructure to maximize the oxygen-water reaction activity. Atom probe tomography and density functional theory calculations reveal that reduced proton adsorption/diffusion energy barriers are triggered by homogeneous ion distributions in the perovskite oxide. Moreover, the thermally driven mild oxygen release can be further offset by beneficial proton uptake, thereby increasing the thermomechanical durability of the oxygen electrode. The resulting R-PCECs obtain a peak power density of 1.56 W cm^-2 and an electrolysis current density of 2.0 A cm^-2@1.3 V at 600 °C while demonstrating long-term stability exceeding 780 hours, with degradation rates of 19.3 and 16.9 μV h^-1 in fuel cell and electrolysis modes, respectively.