Effects of Ir Loading on Nb-Doped SnO ₂ on the Oxygen Evolution Reaction Activity in PEM Water Electrolysis

Iridium oxide (IrOx) catalysts supported on Nb-doped SnO2 (Nb dopant content of 4 at. %) were prepared with different Ir loadings. The microstructure of IrOx on this support material transforms from dispersed nanoparticles into interconnected nanoparticle networks, accompanied by improved conductivity and reduced work function. These electronic and structural evolutions enhance the oxygen evolution reaction (OER) activity, with both mass and specific activities nearly doubling as the Ir loading increases from less than 10 wt % to over 30 wt %. The results highlight how tuning IrOx morphology and interfacial energetics enable efficient OER catalysis at optimized Ir loadings, offering a pathway toward cost-effective and scalable proton exchange membrane (PEM) water electrolysis.