Highly Robust Membrane Electrode Assembly Using Engineered Dual‐Phase Iridium Oxide Catalysts Breaking the Activity–Durability Trade‐Off in Proton Exchange Membrane Water Electrolysis

ABSTRACT Proton exchange membrane water electrolysis (PEMWE) is a compelling route for sustainable green hydrogen production. Yet Ir‐based oxygen evolution reaction (OER) catalysts suffer from a persistent trade‐off between activity and stability under acidic conditions. Amorphous IrO _x displays high intrinsic activity but limited structural resilience, whereas crystalline IrO ₂ affords robustness at the expense of accessible active sites. Reconciling these conflicting properties through rational structural design remains a significant challenge. This study presents a hollow dual‐phase iridium oxide (HDP‐IrO _x ) catalyst comprising coexisting amorphous and crystalline domains, synthesized via polydopamine‐coated polystyrene‐sphere hard templates. Calcination temperature precisely tunes the amorphous–crystalline ratios, while template diameter (190, 240, and 360 nm) controls shell architecture and the extent of amorphous domain formation. The optimized HDP‐IrO _x ‐240 exhibits a low overpotential of 283 mV at 10 mA cm ⁻² in half‐cell evaluation, and HDP‐IrO _x ‐360 achieves 1.77 V at 2 A cm ⁻² in single‐cell operation with remarkable stability (31.5 µV h ⁻¹ decay rate) over 1036 h. Cooperative amorphous–crystalline interactions ensure efficient charge transport while maintaining structural integrity. Dual‐phase engineering thereby establishes an intrinsic design paradigm that reconciles activity and durability. This approach advances next‐generation PEMWE anodes with low Ir loading.