A synergistic architecture design for functionally boosting the hydroxyl adsorption and charge transfer for the oxygen evolution reaction

The adsorption of surface reactant hydroxyl and subsequent charge transfer are the cornerstones of alkaline oxygen evolution reaction (OER). Though exhibiting benign OER performance, the catalytic activity of perovskite oxides is restricted by their inferior specific area and insufficient hydroxyl affinity. Here, a novel architecture composed of a karren structure and hybrid phase was proposed to uplift the kinetic limitation of hydroxyl adsorption and charge transfer. As a proof-of-concept, the karren-structure perovskite-based compound (Pr_0.5Ba_0.25Sr_0.25Co_0.8Fe_0.2O_3−δ-Co₃O₄) synthesized by facile molten-salt synthesis exhibits excellent OER activity with a low overpotential of 360 mV at 10 mA cm⁻² in 0.1 M KOH, and delivers 5-fold mass activity at 1.63 V relative to pristine perovskite Pr_0.5Ba_0.25Sr_0.25Co_0.8Fe_0.2O_3−δ, outperforming various transition metal oxides and noble metal RuO₂. With insights from physicochemical characterization and in situ electrochemical analysis, the interlinked karren structure is effective in providing active area and ion transfer channels for promoting the contact of hydroxyl with active sites, while the strong electronic interaction of the hybrid phase further favors the hydroxyl adsorption and charge transfer, synergistically expediting the sluggish OER kinetics. This work provides insights into the design of perovskite-based electrocatalysts with high performance via a synergistic structural modulation.