Reducing iridium loading in proton exchange membrane water electrolyzer anodes is essential to meet cost targets for large‐scale green hydrogen production. Here, we report a photodeposition‐based synthesis of TiO 2 @IrO 2 core‐shell catalysts with iridium contents as low as 10 wt%. The influence of annealing temperature, iridium content, and iridium loading on structural and electrochemical properties is systematically investigated. An annealing temperature of 450 °C provides the best compromise between activity, conductivity, and stability. Remarkably, even at 10 wt% Ir (≈4.5 vol% IrO 2 ), the core‐shell architecture maintains high electronic conductivity and mass activity. The low iridium content results in ~18 μm thick catalyst layers at a loading of 0.35 mg Ir cm −2 , corresponding to a high thickness factor of 52.0 ± 0.8 μm (mg Ir cm −2 ) −1 . Two‐dimensional, two‐phase performance modeling reveals that these thick catalyst layers improve electronic connectivity at low loadings, leading to higher catalyst utilization than a commercial reference. As a result, the core‐shell catalyst outperforms the reference in single‐cell measurements, achieving 1.77 V at 2 A cm −2 at a low loading of 0.31 mg Ir cm −2 . During 200 h durability testing, reversible degradation is observed, while irreversible losses remain on par with the reference and the core–shell structure is preserved.
Finger et al. (Mon,) studied this question.