Volume Changes Induced by the Electrochromic Process in Sputtered Iridium Oxide Films

We report volume changes induced by the electrochromic process in sputtered iridium oxide films (SIROF's). We show that SIROF's expand on incorporation of water. The rate of water uptake is greatly increased by initial potential cycling, i.e. , coloring and bleaching. Hydration increases the kinetics of electrochromism by about an order of magnitude. We show also that electrochromic coloring and bleaching reversibly modulates the thickness of partially hydrated SIROF's. As‐deposited SIROF's significantly contract upon initial cathodic bleaching which supports the anion mechanism of electrochromism in iridium oxide films.