Rational Design of Atomic Skin Layers with Low Ir–Ir Atomic Distance for Highly Efficient OER Catalysts

• • Ir@KM achieves a low overpotential of ~280 mV at 10 mA cm−2, outperforming conventional IrO2 and reducing energy losses in PEM electrolysis. • • Mass activity reaches 18,500 A gIr−1 at 1.8 V, 17.6 times higher than IrO2, enabling a drastic reduction in Ir loading and cost (73 $ kW−1 vs. 820 $ kW−1 for IrO2). • • The Ir-skin layer is only 1–2 atomic layers thick, with a low Ir–Ir atomic distance that triggers an oxide path mechanism (OPM), lowering theoretical overpotential to 0.13 V. • • Stability tests show a potential decay rate of 0.27 mV h−1 in the first 50 h, stabilizing to −0.12 mV h−1 after startup, with stable operation at 1.5 A cm−2 and minimal Ir/Mn dissolution.