Nano-porous iridium and iridium oxide thin films formed by high efficiency electrodeposition

Abstract

The goal of this work has been to fabricate very thin, highly porous Ir films, of use in a wide variety of applications. To achieve this objective, Ir was electrodeposited on a Au-coated quartz crystal, allowing in situ mass measurements to be carried out while concurrently monitoring the charge passed, as a function of the deposition potential, H₂IrCl₆ concentration, and time. Ir thin films (<5 nm) could be deposited at 100% charge efficiency at an optimum potential of 0.1–0.2 V vs. RHE, all in room temperature 0.5 M H₂SO₄ containing various concentrations of H₂IrCl₆. Field emission scanning electron microscopy and in situ surface area measurements showed that the Ir films are uniform and yet highly porous (up to 50%), independent of film thickness. We were also able to efficiently convert the electrodeposited Ir to Ir oxide, without significant loss of metal or diminished coating adhesion, while also maintaining their very high surface area properties. These interesting thin films are very promising for a wide variety of electrocatalytic and sensing applications.