Developing oxygen evolution reaction (OER) electrocatalysts that can operate at industrial current densities with high activity and long-term stability represents a key challenge for the practical implementation of anion exchange membrane water electrolysis (AEMWE). Herein, we report an Ir-Ni dual-site catalyst constructed via anion-coordination modulation, comprising Ir single atoms anchored on N-doped ultrathin NiO nanosheets (Ir-NiNO/NF) for alkaline OER. The N doping induces charge redistribution, lowers the Ir oxidation state, and optimizes the electronic environment via Ir-N coordination. In-situ Raman measurements reveal that the N doping effectively lowers the formation potential of the NiOOH active species and promotes interfacial charge transfer. Density functional theory calculations combined with in-situ DEMS confirm an oxide pathway mechanism (OPM) on Ir-Ni dual sites, bypassing scaling limitations of the conventional adsorbate evolution mechanism and structural degradation of the lattice oxygen mechanism. The self-supported electrode achieves ultralow overpotentials of 209 and 363 mV at 10 and 500 mA cm^-2. An AEMWE electrolyzer using Ir-NiNO/NF as both diffusion layer and anode requires 1.7 V at 2 A cm^-2 (60 °C) and operates stably for >280 h at 1 A cm^-2. This study provides new insights into low-Ir-loading, high-activity OER catalyst design and dual-site catalytic mechanisms.