A series of bifunctional ReBaCo2O5+ perovskite catalysts towards intermediate-temperature oxygen reduction reaction and oxygen evolution reaction

High-performance electrocatalysts are crucial to accelerate the commercialization of solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs). Herein we develop a series of bifunctional ReBaCo2O5+δ (Re = La, Pr, Nd, Sm, Eu, and Gd) perovskite catalysts, demonstrating both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activity. When varying the rare earth ions, orthorhombic-tetragonal-cubic transformation can be identified in the ReBaCo2O5+δ (ReBCO) family, along with enhanced electrical conductivity, improved oxygen surface exchange and chemical diffusion rates. Through symmetrical half-cell test, as-obtained perovskite electrodes exhibit the area-specific resistances (ASRs) as low as 0.048–0.096 Ω cm2 at 700 °C. In the ORR and OER manners, LaBaCo2O5+δ (LBCO) shows the largest current densities of 314 and 323 mA cm−2 at an overpotential (η) of 75 mV at 700 °C among all compositions. Anode-supported fuel cell with the LBCO cathode delivers a peak power density (PPD) of 1212 mW cm−2 at 750 °C. Aiming at the CO2 electrolysis, a current density of 1.24 A cm−2 is achieved in the LBCO anode-containing cell at 750 °C. From first-principle density functional theory (DFT) calculations, it is inferred that the O 2p-band centers for electron-filled states may be closely correlated with electrocatalytic activity. Our results highlight promising intermediate-temperature applications of LBCO in both SOFC and SOEC models, endowing rational design of the perovskite catalysts in energy conversion field.