An improved method of preparing iridium oxide electrode based on carbonate-melt oxidation mechanism

pH is a fundamental parameter in understanding the chemical processes in many fields. Based on the strong oxidative characteristic of the molten lithium carbonate (Li2CO3), an advanced iridium oxide electrode preparation approach is developed by adding sodium peroxide (Na2O2) powder into a Li2CO3 melt in a semi-closed/closed reactor at a high temperature to increase the regional peroxide (O22−) ion concentration in the iridium-melt interface. The iridium oxide film (IROF) of prepared electrodes has a dense and uniform surface with small and cone-shaped particles. Open-circuit tests show that electrodes exhibit a near-Nernstian pH response with good linearity, fast response, high stability (a slight periodic fluctuation of potential change with standard deviation <0.65 mV in 48 h), good reversibility in the pH range of 2.00-10.00, and anti-interference to low concentration of oxidants. Besides, electrodes show a stable response in seawater, indicating the major ions in seawater do not influence their performances. In addition, prepared electrodes from the same batch show consistency in terms of sensitivity and the intercept of the standard curve (E°'), while electrodes from different batches vary in E°', which could be attributed to the hardness in controlling identical synthetic conditions among fabrications of different batches.