Design of Dual-Phase Iridium Oxide Catalysts Breaking the Activity–Durability Trade-Off in Proton Exchange Membrane Water Electrolysis

Abstract

The accelerating increase in global greenhouse gas emissions has intensified climate change and environmental concerns, thereby driving rapid growth in the demand for renewable energy sources that do not emit carbon. However, the inherent intermittency of renewable power often leads to substantial curtailment, necessitating efficient energy-storage strategies. Converting surplus renewable electricity into hydrogen offers a viable pathway for long-term energy storage, and the resulting product—green hydrogen—has emerged as a key enabler of a sustainable energy economy. Proton exchange membrane water electrolysis (PEMWE) is particularly promising for green-hydrogen production due to its rapid dynamic response and excellent compatibility with fluctuating renewable energy. Nevertheless, PEMWE relies on precious-metal catalysts for the oxygen evolution reaction (OER), creating an urgent need for catalyst designs that minimize Ir loading while maintaining both high performance and long-term durability. Ir-based OER catalysts fundamentally suffer from a persistent trade-off between activity and durability under acidic PEMWE conditions. Amorphous IrOx provides high intrinsic activity due to its abundant unsaturated Ir–O motifs, yet its structural instability leads to rapid degradation. Conversely, crystalline IrO2 offers superior robustness but sacrifices active-site accessibility, resulting in lower catalytic activity. Reconciling these contradictory characteristics within a single catalyst architecture remains one of the central challenges in Ir-based OER catalyst design. In this thesis, we present a hollow dual-phase iridium oxide (HDP-IrOx) catalyst comprising coexisting amorphous and crystalline domains, synthesized using polydopamine-coated polystyrene-sphere hard templates. Calcination temperature enables precise control of the amorphous–crystalline balance, while template diameter (190, 240, and 360 nm) governs shell architecture and the extent of amorphous-domain formation. The optimized HDP-IrOx-240 achieves an overpotential of 283 mV at 10 mA cm-2 in half-cell evaluation, whereas HDP-IrOx-360 delivers outstanding single-cell performance of 1.77 V at 2 A cm-2 with remarkable stability (31.5 μV h-1 decay over 1036 h). These cooperative amorphous–crystalline interactions enable efficient charge transport while preserving structural integrity, establishing dual-phase engineering as a powerful design paradigm for advancing next-generation PEMWE anodes with low Ir loading.