Ultrasmall Ir nanoparticles for efficient acidic electrochemical water splitting

The exploration of highly active catalysts with superior stability for overall water splitting has received considerable attention. Although intensive efforts have been made to design numerous electrocatalysts for water splitting in alkaline media, only a few electrocatalysts have been developed for proton exchange membrane (PEM)-based electrolyzers in acidic media. Herein, we report a colloidal synthesis of well dispersed ultrasmall Ir NPs with narrow size distribution, of superior catalytic activity and stability toward HER and OER in acidic media. When further used as both an anode and a cathode for acidic overall water splitting, the as-synthesized monodisperse Ir NPs yield a current density of 10 mA cm−2 at 1.58 V with long-term stability.