The Electrochemistry of Iridium Oxide Films in Some Nonaqueous Solvents

Ir oxide films, grown in aqueous solutions , have been found to exhibit excellent charge capacities, charging and discharging kinetics, and stability in acetonitrile and propylene carbonate with as the supporting electrolyte, while the results in THF also appear to be quite promising. The oxide is electrochromic in all of these media. In order to obtain the optimum response of Ir oxide in nonaqueous solutions, it is important to prevent the drying out of the oxide when transferring it from the aqueous to nonaqueous media. Discharging and charging of the oxide appears to involve Li + insertion and expulsion from the oxide, respectively. Oxides formed in neutral aqueous solutions have been found to be mechanically more stable than those grown in aqueous or in 50% aqueous . This is supported by SEM evidence of a less cracked and more adherent Ir oxide film when grown in neutral aqueous solutions, as compared to the case in the latter solutions.