Precise control of composition and morphology is critical for high-performance oxygen evolution reaction (OER) catalysts. Herein, Co₀.₅Fe₀.₅ Prussian Blue Analogues (PBAs) with hollow nanocube morphology are synthesized by tuning the Co/Fe ratio, enhancing active site exposure and electronic structure. Electrochemical evaluation in 1.0 M KOH reveals an overpotential of 266 mV at 10 mA cm⁻², a Tafel slope of ~30 mV dec⁻¹, and excellent stability over 90 h.
Density functional theory (DFT) calculations show that the (100) crystal plane of KₓFe₄[Co(CN)₆]₃·6H₂O (x = 1–4) with embedded alkali cations reconstructs into an Fe₀.₅Co₀.₅OOH layer with OH vacancies, representing the active OER surface. Increasing alkali cation concentration, induces lattice distortion and closer cation penetration toward the Fe₀.₅Co₀.₅OOH layer. Projected density of states (PDOS) analysis shows that O 2p states shift toward the Fermi level with increasing cation content, increasing non-bonding states for the Fe0.5Co0.5OOH formed on top of KFe4[Co(CN)6]3·6H2O and K2Fe4[Co(CN)6]3·6H2O, consistent with a lattice oxygen-mediated mechanism (LOM) for enhanced OER activity. The theoretical calculation results well align with the experimental linear scanning voltammetry (LSV) curves. This work demonstrates that atomic-level engineering of Co–Fe PBAs enables synergistic tuning of morphology and electronic structure, offering a promising strategy for designing high-performance OER electrocatalysts.