Monolayer Iridium Nanoparticles Coated TiO 2 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.