Percolation-driven iridium nanotube network linking utilization and durability for oxygen evolution electrode in proton exchange membrane water electrolysis

The high cost and limited availability of iridium restrict large-scale deployment of proton-exchange-membrane water electrolyzers (PEMWEs). Addressing this challenge requires maintaining electronic connectivity and catalytic activity at low Ir loadings. This study introduces an ionomer-free, iridium nanotube (IrNT) network that forms a contiguous one-dimensional electronic scaffold coated onto a titanium porous transport layer. IrNTs reach electrical percolation at an order-of-magnitude lower loading than IrO 2 nanoparticles (L c = 31.3 vs. 350.1 µg cm⁻²), boosting current distribution and Ir utilization at ultralow loadings. This enables mass activity to maximize at 50 µg cm -2 , reaching 79.03 A mg -1 . Durability testing up to 960 h identifies a two-step degradation pathway: (i) nanotube-to-nanoparticle morphological deformation that primarily elevates mass-transport resistance, follo…