Connected iridium nanoparticle catalysts coated onto silica with high density for oxygen evolution in polymer electrolyte water electrolysis.

We propose connected Ir nanoparticle catalysts (Ir/SiO 2 ) by coating 1.8 nm Ir particles with high density onto silica for the oxygen evolution reaction. Nanoparticles form electron-conducting networks, which can eliminate the need for an electron-conducting support. Ir/SiO 2 showed a high electrochemical surface area, mass activity, and water electrolysis performance.