Ir Supported by Mesoporous SiO<sub>2</sub> (SBA15) as the Catalyst for Proton Exchange Membrane Water Electrolyzer

The oxygen evolution reaction (OER) is a critical process in proton exchange membrane (PEM) water electrolysis, but its sluggish kinetics and harsh operational environment e.g., high anodic potentials, oxidative atmosphere, and strong acidic media pose significant challenges to catalyst design. Iridium (Ir) is among the most effective catalysts for OER in acidic conditions; however, its scarcity and high cost necessitate strategies to enhance its efficiency and stability. Reducing the size of Ir nanoparticle to 3-4 nm can significantly enhance OER activity due to an increased surface area and more accessible active sites. In this study, we report the synthesis of a highly active and stable Ir/SBA15 catalyst, in which Ir nanoparticles are uniformly deposited onto mesoporous silica (SBA15). The mesoporous structure of SBA-15 facilitates uniform nanoparticle dispersion, while the incorporation of a conductive nanochain structure enhances electronic conductivity. Transmission electron microscopy (TEM) confirmed the uniform distribution of Ir nanoparticles with an average size of 3-4 nm. Electrochemical tests revealed that Ir/SBA15 exhibits high OER activity, excellent cycling stability, and improved conductivity compared to conventional Ir catalysts. These findings demonstrate that SBA15 supported Ir nanochains offer a promising pathway for efficient and durable OER catalysis in PEM electrolyzers, achieving a balance between catalytic performance, structural integrity, and long-term operational stability.