Controlled Deposition of Iridium Oxide Nanoparticles on Graphene

For hydrogen production by water electrolyzers, iridium dioxide (IrO2) works as a catalyst for oxygen evolution reaction (OER) at an anode. In this report, we aim to study the formation mechanism of IrO2 nanoparticles on graphene by inducing nanoscale defects artificially. The defects on graphene grown on a copper foil by chemical vapor deposition were created by UV-ozone treatment, and IrO2 nanoparticles were deposited by hydrothermal synthesis method. We investigated the amount of defects and oxygen-functional groups on graphene by Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The size and distribution of defects and IrO2 nanoparticles on graphene were analyzed by atomic force microscopy (AFM). Raman spectroscopy and XPS measurement showed that defects and oxygen-functional groups increased with the UV-ozone treatment time. The size of IrO2 nanoparticles was reduced to ca. 4.5 nm on defective graphene, whereas the nanoparticles deposited on pristine graphene is ca. 8.8 nm in diameter. It is found that the IrO2 nanoparticles were deposited and anchored on the edge of hole-like defects on graphene. In addition, the size of deposited nanoparticles can be controlled by the extent of modification in graphene.