Self-assembled PrBaCo2O5+δ–Ba0.9CoO3−δ composite as a highly active and durable oxygen electrode for reversible solid oxide cells

Abstract

A-site layered double perovskite PrBaCo₂O_5+δ (PBC) is a potential oxygen electrode for reversible solid oxide cells. However, the two-dimensional ion transport path and Ba element segregation in PBC limit the electrode reaction kinetics and cause performance degradation. Herein, a self-assembled PBC–Ba_0.9CoO_3−δ (B9C) composite is proposed as a highly active and stable oxygen electrode. The B9C phase with high oxygen vacancies significantly accelerates the oxygen surface exchange kinetics and promotes the oxygen transport between anisotropic PBC phase particles. Meanwhile, a misfit dislocation interface is formed due to the lattice mismatch between the PBC and B9C phases. This interface provides tensile stress on the PBC phase and thus releases the lattice compressive stress on the Ba ions, thereby mitigating Ba segregation and enhancing chemical stability. Consequently, the designed PBC–B9C electrode realizes a low polarization resistance of 0.054 Ω cm² at 650 °C, and the constructed single cell exhibits superior operational stability, with low degradation rates of 1.2 × 10⁻¹ mV h⁻¹ and 3.9 × 10⁻¹ mV h⁻¹ in fuel cell and electrolysis cell modes, respectively.