Selective Cobalt-Mediated Formation of Hydrogen Peroxide from Water under Mild Conditions via Ligand Redox Non-Innocence

Despite the broad importance of hydrogen peroxide (H₂O₂) in oxidative transformations, there are comparatively few viable routes for its production. The majority of commercial H₂O₂ is currently produced by the stepwise reduction of dioxygen (O₂) via the anthraquinone process, but direct electrochemical formation from water (H₂O) would have several advantages─namely, avoiding flammable gases or stepwise separations. However, the selective oxidation of H₂O to form H₂O₂ over the thermodynamically favored product of O₂ is a difficult synthetic challenge. Here, we present a molecular H₂O oxidation system with excellent selectivity for H₂O₂ that functions both stoichiometrically and catalytically. We observe high efficiency for electrocatalytic H₂O₂ production at low overpotential with no O₂ observed under any conditions. Mechanistic studies with both calculations and kinetic analyses from isolated intermediates suggest that H₂O₂ formation occurs in a bimolecular fashion via a dinuclear H₂O₂-bridged intermediate with an important role for a redox non-innocent ligand. This system showcases the ability of metal-ligand cooperativity and strategic design of the secondary coordination sphere to promote kinetically and thermodynamically challenging selectivity in oxidative catalysis.