Monolayer Iridium Nanoparticles Coated TiO2 Core‐Shell Architecture as Efficient Oxygen Evolution Reaction Electrocatalyst

Abstract Reducing the noble metal loading of oxygen evolution reaction (OER) electrocatalyst for polymer electrolyte membrane electrolyzers is a necessity for enabling their large‐scale deployment for hydrogen production. This work introduces a highly active and stable OER catalyst which is based on a core‐shell architecture by covering a monodispersed layer of iridium nanoparticles on the core of TiO 2 using a one‐step polyol reduction method. The monolayer of iridium coating is substantiated by analyzing the accurate loading from inductively coupled plasma mass spectrometry (ICP‐MS) combined with morphology/size from transmission electron microscopy (TEM) and the theoretical model of the most‐dense arrangement of iridium nanoparticles on TiO 2 surface. The conductive network constructed by interconnected iridium nanoparticles on the surface together with full participation of iridium atoms in the catalytic reaction benefitting from the less than 2 nm size and monolayer adsorption of iridium nanoparticles endow the catalyst with extremely high OER activity (486 A g Ir −1 at 1.5 V vs RHE) and stability (100 h at 10 mA cm −2 ). This work shows a new way to prepare iridium‐based electrocatalysts with high mass activity.