Smart Compositional Design of B-Site Ordered Double Perovskite for Advanced Oxygen Catalysis at Ultra-High Current Densities

Abstract

Perovskite oxides have been considered promising oxygen catalysts for oxygen reduction and evolution reactions (ORR and OER), owing to structural and compositional flexibility, and tailorable properties. Ingenious B-site ordered La_1.5Sr_0.5NiMn_0.5Fe_0.5O₆ (LSNMF) double perovskite is strategically designed by simultaneously interposing Ni_0.5Mn_0.5 and Ni_0.5Fe_0.5 into B′ and B″ sites. Controlling B-site cation systematically tailors the electronic structure of the B-site cation with a d-band center (M_d) upshift close to the Fermi level, increasing the overlap of the M_d center and O 2p center (O_P). The strong interaction of M_d and O_p facilitates the adsorption of oxygen and activates the lattice oxygen to participate in the OER process, thereby enhancing the ORR and OER activity. For ORR, LSNMF exhibited an onset potential of 0.9 V along with a high limiting current of −8.05 mA cm⁻². At the same time, for OER at 1 m KOH, LSNMF effectively reached a maximum current density of 3000 mA cm⁻². Most importantly, the difference between E_ORR (at −1 mA cm⁻²) and E_OER (at 10 mA cm⁻²), ΔE is 0.69 V, which stands among the best of recently reported perovskites. The as-designed LSNMF is stable, efficient, lucrative, and a promising candidate for practical application.