Discovering the pH-independent Oxygen-Oxygen Formation via Direct Mn-oxo Coupling

Unraveling the mechanism of O─O bond formation on metal-oxo is critical yet remains a central challenge in electrocatalytic water oxidation. Herein, we show the pH-independent O─O bond formation pathway in edge-shared dual [MnO₆] motifs. By manipulating the atomic-scale connectivity of [MnO₆] units, two structurally well-defined sodium manganese pyrophosphate compounds with edge-sharing (Mn-edge) and corner-sharing (Mn-corner) [MnO₆] octahedral configurations were synthesized with similar chemical composition and morphology, except that the Mn ∼ Mn distance in Mn-edge is significantly shorter than that in Mn-corner. Electrochemical and spectroscopic analyses reveal that Mn-edge exhibits an unprecedented pH-independent evolution of O₂. Isotope-labeling experiments and in situ Raman spectroscopy identify a direct coupling mechanism between Mn-O species in Mn-edge, bypassing the conventional nucleophilic water attack. Density functional theory calculations further support that Mn-oxo coupling between asymmetric Mn^VI ∼ Mn^V centers drastically reduces the energy barrier for O─O bond formation. These findings establish the connectivity of [MnO₆] as a critical descriptor for water oxidation mechanism and offer a new design strategy for efficient catalysts inspired by natural oxygen-evolving complexes.