Improved iridium/iridium oxide pH electrode through supercritical treatment

pH measurement has received extensive attention from researchers in numerous fields including medical diagnostics agriculture, food industry, marine, and chemical engineering. Owing to their electrode stability, drift degree, and preparation process, iridium/iridium oxide electrodes are considered as the most promising candidate for pH detection under these conditions. In this study, iridium/iridium oxide electrodes were fabricated by thermal cycling oxidation method. The relationship between the electrode structure and performance was investigated and discussed. To study the influence of supercritical treatment, the as-prepared electrodes were treated at 35 MPa and 400 °C for 3 h. After examining their pH response, the supercritically treated electrodes exhibit better performance than the untreated iridium/iridium oxide electrodes. The structural changes of the treated electrodes were investigated by Raman spectroscopy, X-ray photoelectron spectroscopy, cyclic voltammograms and scanning electron microscopy. The results revealed the important changes in the iridium oxide film of the electrode after supercritical treatment, such as its morphology, chemical bond, valence state, and defects, which collaborated to achieve its improved performance.