Constructing an active and stable oxygen electrode surface for reversible protonic ceramic electrochemical cells

The reversible protonic ceramic electrochemical cells (R-PCECs) can efficiently and cost-effectively store and convert energy at low-intermediate temperatures (400-700 oC). Their widespread commercialization is mainly limited by the challenges of oxygen electrodes due to the slow oxygen reaction kinetics and poor durability. In this study, we first enhance the reaction activity and surface stability of a double-perovskite PrBaCo2O5+δ (PBC) oxygen electrode by employing a fluorite-based Pr0.1Ce0.9O2+δ (PCO) catalyst coating. The PCO-coated PBC (PCO-PBC) oxygen electrode shows a much-reduced area-specific resistance of 0.096 Ωcm2 and good performance on a fuel-electrode supported single cell at 650 oC, displaying a typical peak power density of 1.21 Wcm-2 (in fuel cell mode) and a typical current density of 2.69 Acm-2 at 1.3 V (in electrolysis mode) with reasonable faradaic efficiencies and durability. PCO coating has significantly improved the surface exchange process, facilitated ion diffusion, and suppressed the Ba-segregation of PBC, as confirmed by the analyses of electrochemical performance and TEM.