Synergistic modulation of electronic structure in high entropy perovskite oxide for enhanced bifuntional oxygen evolution/reduction reactions and its mechanistic insights via in-situ analyses and density functional theory calculation

The development of high-performance bifunctional electrocatalysts for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is crucial for advancing energy conversion technologies. Here, we introduce sulfur-doped La_0.8Sr_0.2(CrMnFeCoNi)O₃ high-entropy perovskite oxides (HEPOs) as effective bifunctional OER/ORR electrocatalysts. Through well-designed manipulation of the A-site, B-site, and oxygen-site atoms, the electronic structure of the resulting S-doped HEPO is synergistically modulated to enhance bifunctional catalytic activity. The obtained LS5M-3S demonstrates an excellent bifunctionality, with an OER overpotential of 384 mV at 10 mA cm⁻² and an ORR half-wave potential of 0.731 V in a 0.1 M KOH electrolyte. Advanced in-situ analyses, including liquid cell transmission electron microscopy, synchrotron X-ray absorption spectroscopy, and Raman spectroscopy, combined with density functional theory calculations, were conducted to elucidate the mechanistic insights into the adsorbate evolution mechanism and lattice oxygen-mediated mechanism (LOM) dual reaction pathways in the LS5M-3S sample. Mn, Fe, Co, and Ni act as co-active sites for OER, while Mn, Fe, and Co primarily drive ORR activity. Additionally, oxygen vacancies facilitate the LOM mechanism by promoting lattice oxygen participation. Our results demonstrate that the LOM predominantly governs the reaction. These findings pave the way for designing next-generation, high-performance bifunctional catalysts.