Breaking Scaling Relations via Constructing Short Ir‐O‐Cr Asymmetric Units to Trigger O‐O Coupling in Oxygen Evolution

ABSTRACT The scaling relations among oxygenated intermediates constrain a thermodynamic limitation on the oxygen evolution reaction (OER) in proton exchange membrane water electrolysis (PEMWE). Herein, we break this limitation via Cr doping into iridium oxide, which induces compressive strain and constructs short, distorted Ir‐O‐Cr asymmetric units with a shortened Ir‐Cr distance. This structure configuration enables direct O‐O coupling during OER catalysis, which activates oxygen path mechanism (OPM) and thus circumvents the scaling‐relation‐limited step of conventional adsorbate evolution mechanism. Charge transfer from Cr to Ir downshifts the Ir d‐band center and enhances Ir‐O covalency, which lowers the kinetic barrier for oxygen intermediates formation. Moreover, Cr doping strengthens the interfacial hydrogen‐bond network, facilitating proton diffusion and thus mitigating catalyst degradation caused by local proton accumulation. The obtained catalyst delivers a low overpotential of 223 mV at 10 mA cm −2 and operates stably over 300 h, significantly outperforming commercial IrO 2 (271 mV, 7 h). The catalyst‐based PEMWE delivers a high current density of 3 A cm −2 at 2.05 V and shows stable performance under practical operations. This work provides an effective strategy to activate OPM pathway through constructing asymmetric units for efficient OER catalysts beyond scaling relations.