Investigations of the Hydration Effects on Cyclic Thermo-Oxidized Ir/IrOx Electrode

Our previous work reported a promising Ir/IrOx electrode developed by cycling heat treatment and quenching process for three times. Hydration is the final process in fabrication, and even an unavoidable process in maintenance and application of Ir/IrOx electrode. The effects of hydration on Ir/IrOx electrode were examined intensively by various state-of-the-art techniques. XRD and TEM tests manifested that hydration of the IrOx film caused decrease in interplanar spacing and increase in grain size. The relief of tensile stress in IrOx film after hydration was revealed by XRD stress analysis. Raman spectra illustrated an enhancement in the integrity of the surface crystals during the hydration process. It is shown that the unhydrated electrode surface was made up of IrOx with different iridium valences, while Ir(OH)n and the corresponding hydrates appeared after hydration. SIMS, XPS and the related etching showed the different hydration degrees along the direction of oxide surface to substrate. Finally, the possible influence of hydration on the potential of H+ response electrode was discussed, suggesting that an efficient hydration may reduce the drift of electrode potential in long term application.