Tuning and Shielding Iridium Active Sites Through Tungsten Electron Buffer for Oxygen Evolution Catalysis

Efficient and durable oxygen evolution reaction (OER) electrocatalysts under acidic conditions are pivotal for proton-exchange-membrane water electrolysis (PEMWE), yet Ir-based catalysts suffer from activity-stability trade-offs caused by facile over-oxidation and corrosion. Herein, IrO_x nanoclusters decorated with W single atoms (W SAs) and supported on N-doped graphene (defined as W-IrO_x/NG) are synthesized via solvothermal reaction and NH₃-assisted pyrolysis process. In W-IrO_x/NG, W SAs with W–N₃O₁ configuration are attached onto IrO_x nanoclusters through W─O─Ir linkers, forming interfacial covalent connections for efficient charge transfer. W-IrO_x/NG delivers an ultrahigh mass activity of 2998.91 A g_Ir⁻¹ at 300 mV overpotential and maintains stable operation for over 250 h at 1 A cm⁻² in a PEM electrolyzer with an ultralow Ir loading (0.25 mg_Ir cm⁻²). Mechanistic insight analysis uncovers that W atoms serve as electron buffer, donating and storing electrons to regulate the oxidation state of Ir during OER, thereby suppressing irreversible over-oxidation. Theoretical calculation demonstrates that W SAs with W─N₃O₁ sites modulate the d-band structure of Ir center, lowering the deprotonation barrier of *OH/*OOH intermediates and simultaneously weakening oxo-species adsorption strength, thus accelerating OER kinetics.