Breaking linear scaling relationships in acidic water oxidation via engineered molecular Co-catalysts

Abstract

The oxygen evolution reaction (OER) critically governs the efficiency of proton exchange membrane water electrolysis (PEMWE), yet its kinetics remain constrained by energy-scaling relationships. This work reports on an oxyanion-modification-induced hydrogen-bond-assisted adsorbate evolution mechanism that significantly boosts the performance of the acidic OER. Single-atom Zn and lattice S are designed as cation–anion pairs to co-stabilize the SO₄²⁻ groups. The optimized Zn₁/RuS_yO_2–x–SO₄ achieves a low overpotential of 158 mV at 10 mA cm⁻² and outstanding stability during a continuous 235-h test in a 0.5 M H₂SO₄ electrolyte. Operando spectroscopy and theoretical calculations reveal that SO₄²⁻ species significantly lower the energy barrier of the rate-determining step in the adsorbate evolution mechanism by forming hydrogen bonds with key *OOH intermediates, thereby circumventing the typical scaling limitations. Concurrently, the formation of hydrogen bonds and strong electronic interactions between the SO₄²⁻ groups and water molecules promote water adsorption and accumulation on the Zn₁/RuS_yO_2–x–SO₄ surface, further enhancing the reaction kinetics. Moreover, the incorporated SO₄²⁻ groups significantly impede lattice O loss and Ru dissolution, extending the durability of Zn₁/RuS_yO_2–x–SO₄ during acidic OERs. This study provides a novel cation–anion co-anchoring oxyanion strategy to overcome existing energy-scaling constraints, enabling a more efficient Ru-based catalyst for PEMWE application.