Electrodeposition of Iridium in 1-Butyl-3-Methylimidazolium Tetrafluoroborate Ionic Liquid

The electrochemical behaviors of iridium electrodeposited in 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid were studied. Cyclic voltammograms prepared on the gold electrode suggested that Ir(III) was reduced to iridium with an irreversible one-step process, which was controlled by the diffusion of Ir(III). The diffusion rate is 3.83×10−11 m2/s and the average transfer coefficient is 0.083. The morphology of iridium coatings prepared on molybdenum substrates was observed by scanning electron microscopy (SEM), and the composition was characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Results show that the morphologies of iridium coatings is dependent on the potential, the time and the current density of electrodeposition. Compact coatings are obtained at the reduction peak potential with a balance between the nucleation rate and the growth rate. Flat and compact coatings are formed when the current density ranges from 0.5 mA/cm2 to 1.82 mA/cm2 in the galvanostatic electrodeposition.