Constructing Asymmetric Ir‐O‐Ru Unit to Promote Rapid Deprotonation and Stable Lattice Oxygen in PbIrRu Pyrochlores for Water Oxidation

Exploring efficient and durable low‐iridium (Ir) catalysts for the oxygen evolution reaction (OER) is crucial for the commercialization of proton exchange membrane water electrolysis (PEMWE). Herein, asymmetric Ir‐O‐Ru active units are constructed in PbIrRu pyrochlore (Pb2(IrRu)2O7−δ) by incorporating ruthenium (Ru) sites into PbIr pyrochlore through a scalable hydrothermal strategy. Soft X‐ray absorption spectroscopy, operando characterizations, and DFT calculations reveal that the Ir‐O‐Ru units promote rapid deprotonation of oxo‐intermediates (*OH→*O) for enhancing OER kinetics by modulating charge distribution of oxygen through breaking bridged‐oxygen symmetry in [IrO6] octahedral units. Operando differential electrochemical mass spectrometry demonstrates that these asymmetric units also stabilize lattice oxygen during OER catalysis by strengthening metal‐oxygen bonds, which suppresses metal oxidation/dissolution and thus contributes to a superior OER durability. The optimized Pb2(IrRu)2O7−δ exhibits a low overpotential of 188 mV at 10 mA cm−2 and a large mass activity of 1290.2 A g−1Ir+Ru (16.4 and 46.7 times that of commercial IrO2 and RuO2, respectively) in 0.5 m H2SO4. The assembled PEMWE with anode loading of ∼0.36 mgIr+Ru cm−2 achieves 1 A cm−2 at 1.72 V and durably operates for 300 h at high current density with negligible attenuation. This work provides new insights into designing high‐performance pyrochlore‐based low‐Ir catalysts for PEMWE applications.