Insight into Factors Influencing Thermal Oxidation of Iridium Oxide Electrode: Thermostatic Post-Treatment Temperature

Abstract

pH detection of strict environments such as deep sea environment, extremely acid or alkaline environment etc. put forward high requirements for pH monitoring electrode. In this paper, the IrOx electrodes prepared by cyclic thermal oxidation and quenching process (CHQ) went through thermostatic posttreatment process, i.e., heat treatment at the temperature of 400 °C, 500 °C, 600 °C for 0.5 h with furnace cooling to room temperature further. Aiming at filtrating an optimal posttreatment process and improving the comprehensive properties of the IrOx electrodes, the E-pH relationship, potential-time dependence tests, and long-term stability tests were carried out. Further characterizations including surface morphologies, surface roughness, surface crystal qualities, and surface compositions were examined through advanced detection methods. The results indicate that the IrOx electrode went through thermostatic posttreatment at 400 °C has larger surface roughness and relatively smaller cracks, implying the increasement in active surface area for electrode reaction. Optimal percentage of Ir4+and Ir3+ revealed by the X-ray photoelectron spectroscopy (XPS), better crystal quality shown by Raman spectroscopy, relief of tensile stress in the surface film demonstrated by (X-ray diffraction) XRD and Raman could account for the excellent performance of the posttreatment IrOx electrode.