Br‐Mediated Interfacial Microenvironment Engineering Triggers Dual‐Site Oxide Pathway Mechanism for Stable Oxygen Evolution

ABSTRACT Steering the oxygen evolution reaction (OER) toward desired oxide pathway mechanism (OPM) is critical for reconciling catalytic activity and stability. However, rationally triggering the adjacent oxygen‐radical coupling involved in OPM remains highly challenging due to the complex intermediate evolution and the stringent requirement for adjacent dual sites. Herein, we report a Br‐mediated anode‐electrolyte microenvironment engineering to construct a high‐density active •O interface on NiFe oxide, enabling direct •O─O• radical coupling on Ni─Fe dual sites. Rather than simply tuning dual‐site spacing, Br species with large size and weak hydration ability act as interfacial regulators to enhance the Lewis acidity of Ni─Fe centers and reorganize the interfacial hydrogen‐bond network, accelerating OH − migration, adsorption, and •OH deprotonation. The promoted •OH deprotonation shifts the rate‐determining step to •OOH formation and creates a •O‐rich interfacial environment, promoting access to an additional OPM pathway, as verified by in situ ATR‐SEIRAS, DEMS, and DFT calculations. Consequently, NiFeO x Br y exhibits an 89 mV reduction in overpotential at 10 mA cm −2 and requires a cell voltage of only 1.725 V to achieve 1 A cm −2 when employed in an anion exchange membrane electrolyzer. This work establishes interfacial microenvironment engineering as a pathway‐selective design principle for efficient and durable OER catalysis.