Oxyanions stabilized low-coordinated nickel species for efficient and durable nucleophilic electrooxidation.

Abstract

Nucleophilic oxidation reactions (NORs) are key for high-value organics in electrosynthesis, but limited by slow dehydrogenation kinetics and competing oxygen evolution reactions (OER). While low-coordinated Ni species exhibit enhanced activity in rate-determining electrochemical deprotonation, they suffer irreversible oxidation with rapid performance degradation. Herein, we develop a class of oxyanion-stabilized low-coordinated Ni catalysts for highly efficient and durable oxidation of diverse nucleophiles including urea, methanol, and biomass-derived 5-hydroxymethylfurfural. Bicarbonate ligands form an electrostatically repulsive microenvironment, suppressing parasitic OER and Ni over-oxidation via dynamic ligand-cation coordination. These mediators form bifunctional channels, linking Ni^2-δ/Ni^3-δ reversible transition-based deprotonation and nucleophilic H-transfer, boosting dehydrogenation. A prototype catalyst engineered with bicarbonate ligands via electrochemical pre-reduction achieves 500 mA cm^-2 at 1.42 V (versus reversible hydrogen electrode) for urea oxidation and sustains stability for 1100 hours at 100 mA cm^-2. Scaling to 100 cm² anion-exchange membrane reactor yields H₂ and valorized organics, showing sustainable electrosynthesis potential.