Steam-promoted symmetry optimizations of perovskite electrodes for protonic ceramic cells†

Perovskite oxides have attracted considerable attention because of their intriguing properties in electrocatalysis, photocatalysis, and membrane-catalysis for energy storage/conversion. Optimization of their crystal symmetry in tuning electrocatalytic activity within the lattice is effective but challenging. In this study, a delicate steam-promoted symmetry optimization of a perovskite oxygen electrode, Pr_0.5Ba_1/6Sr_1/6Ca_1/6CoO_3−δ (PBSCC), was performed, which resulted in remarkable electrochemical performance and durability. Under typical operating conditions of protonic ceramic cells, the injection of steam into the lattices may promote the transformation of the monoclinic structure into a stable cubic PBSCC perovskite structure with higher symmetry. A protonic ceramic cell with PBSCC oxygen electrodes demonstrated encouraging performance at 650 °C: a peak power density of 2.44 W cm⁻² in fuel cell mode and a current density of 3.79 A cm⁻² at 1.3 V in electrolysis mode. Furthermore, the cell demonstrated promising durability in multiple operating modes for over 500 h at 600 °C.