Iridium-based catalysts supported on corrosion-resistant metal oxides such as TiO₂ are promising candidates for the oxygen

evolution reaction in proton exchange membrane water electrolyzers (PEMWEs). However, the inherently poor electronic

conductivity of oxide supports can limit catalyst performance, especially at low Ir loadings. In this study, we systematically

investigate the relationship between Ir loading, electronic conductivity, and electrochemical activity in Ir-TiO₂ catalysts.

Through structural characterization, electrochemical analysis, and impedance spectroscopy, we demonstrate that insufficient

Ir loading leads to isolated nanoparticles and poor interparticle electron transport, which cannot be fully corrected by

conventional iR compensation methods. Electrochemical impedance spectroscopy reveals that the increased charge transfer

resistance at OER potentials is strongly coupled with limited electronic conductivity. The introduction of conductive carbon

additives restores activity in low-loading systems, confirming the importance of continuous conductive networks. Our

findings highlight a critical design principle: the need to balance Ir utilization and electron transport to maximize catalytic

activity. This work provides a practical framework for diagnosing and overcoming conductivity-related limitations in low-Ir

electrocatalyst systems for PEMWE applications.