Improvement of the Ir/IrO₂ pH electrode via hydrothermal treatment

Several Ir/IrO₂ pH electrodes were prepared by a cyclic thermal oxidation process via dip-coating in a concentrated solution of NaOH. A hydrothermal hydration treatment at 220 °C for 24 h was used to address the problematic potential drift that is common in Ir/IrO₂ pH electrodes. The electrodes that were treated by the hydrothermal method exhibited good stability and high sensitivity compared to those that were hydrated at room temperature. The reasons for this improvement were investigated by Raman spectroscopy, X-ray photoelectron spectroscopy, and field emission scanning electron microscopy. The results suggested that the hydrothermally treated electrode had a more orderly crystal arrangement and a higher content of OH⁻ groups, which drove improvements in the performance of electrode by modification of the Ir/IrO₂ structure. The relationship between the electrode structure and performance was investigated and discussed in detail herein.