Electrochromic Mechanism of IrO[sub 2] Prepared by Pulsed Anodic Electrodeposition

The electrochromic mechanism of IrO 2 thin films was investigated with electrochemical quartz crystal microbalance and surface analyses such as X-ray photoelectron spectroscopy, Auger electron spectroscopy, and scanning electron microscopy. Prior to pulsed anodic current electrodeposition of IrO 2 thin film on indium-tin oxide substrate (total anodic charge 100 mC/cm 2 ), IrO 2 islands, which work as good adhesive seeds, were prepared by cyclic voltammetry. In phosphate buffered saline solution, IrO 2 exhibited blue and black anodic electrochromic behavior at two oxidation potentials of +0.5 and +0.9 V ( vs. a saturated calomel electrode). Surface analysis and mass variations of IrO 2 thin film indicated that the ejection of H + and the injection of Na + caused the cracks in the film and resulted in coloring behaviors.