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

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 IrO₂ 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.