K ⁺ ‐Intercalation Engineering of 1D Ultrathin K _0.25 IrO ₂ Electrocatalyst for Industry‐Level Proton Exchange Membrane Water Electrolysis

ABSTRACT Both commercial and lab‐synthesized IrO ₂ nanocrystals are crucial for acidic oxygen evolution reaction, which remain severely limited in practical proton exchange membrane water electrolysis (PEMWE) by the high overpotential and low stability. Here, we successfully construct 1D K _0.25 IrO ₂ nanocrystal via K ⁺ Intercalation. Novel crystal structure will bring about novel catalytic property. Compared to traditional rutile‐type IrO ₂ , DFT calculations reveal that the lattice regulation via K ⁺ Intercalation lowers the energy barrier for OER and further optimizes the adsorption energy of oxygen intermediates. Therefore, 1D K _0.25 IrO ₂ presents an ultralow overpotential of 237 mV at 10 mA cm _geo ⁻² in a three‐electrode cell, and performs excellent PEM activity with a low E _cell of 1.70 V at 2 A cm _geo ⁻² . More importantly, the practical operating stability of the 1D K _0.25 IrO ₂ anode cell has been demonstrated under both industry‐level constant and dynamic operating conditions. This work develops a novel K ⁺ ‐intercalation engineering for the precise synthesis of 1D ultrathin K _0.25 IrO ₂ electrocatalyst, exhibiting outstanding OER activity and stability in PEMWEs from steady‐state to fluctuating power inputs.