Ru/RuO 2 Heterostructures for Stable and Active Acidic Water Oxidation via Interfacial Charge Redistribution and Lattice‐Oxygen Participation

ABSTRACT The rational design and synthesis of Ir‐free acidic oxygen evolution catalysts combining high activity with long‐term durability remains a formidable challenge. This work demonstrates an addressable and dopant‐free strategy through the construction of Ru/RuO 2 heterostructures in a solely Ru‐based system, wherein interfacial charge redistribution and lattice‐oxygen participation jointly promote catalytic enhancement. The catalyst delivers an overpotential of 182 mV at 10 mA·cm −2 and retains operational durability for over 270 h at 100 mA·cm −2 in 0.5 M H 2 SO 4 . Spectroscopic characterizations, including X‐ray absorption spectroscopy (XAS), Raman spectroscopy, and X‐ray photoelectron spectroscopy (XPS), coupled with theoretical calculations, elucidate that interfacial electron transfer from metallic‐Ru phase to RuO 2 phase, assisted by the formation of a built‐in electric field, results in increased work functions across the heterointerface and lowered interfacial Ru oxidation states, suppressing Ru‐site overoxidation into soluble RuO 4 and accounting for the exceptional durability. Lattice‐oxygen participation, which corresponds to excellent activity, was verified by operando investigations, including differential electrochemical mass spectrometry (DEMS), attenuated total reflection surface‐enhanced infrared absorption spectroscopy (ATR‐SEIRAS), and tetramethylammonium (TMA + ) chemical probing. The overall findings establish heterointerface engineering as a powerful tool for the simultaneous enhancement of the coupled activity‐stability in Ru‐based acidic OER catalysts.