The Effects of Cyclic Isothermal Oxidation on Ir/IrOx pH Electrode and a Method to Correct the Potential Drift of Metal Oxide Electrode

The present work demonstrated the effects of isothermal oxidation temperature (750 degrees C similar to 870 degrees C) and water quenching cycle times (1 similar to 3) on properties of IrOx pH electrodes. Property tests of the fabricated electrodes showed that electrodes developed by 800 degrees C isothermal heating and water quenching for 3 times (H&Q 3) had excellent near Nernst E-pH relationship, relatively faster response rate and the minimum potential drift in long-term stability test. Surface and cross-section morphologies, confocal laser scanning microscopy, electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS) were employed to characterize the electrodes to explore the reason for their excellent properties. Surface morphology showed that the iridium oxide film (IROF) made by H&Q 3 at 800 degrees C had larger surface roughness, and well-defined homogeneous dense inner layer and loose porous outer layer. Besides, it had the minimum reaction resistance in both acid and alkaline buffers, and contained more effective compositions compared to electrodes fabricated by other conditions. Thus H&Q 3 at 800 degrees C was suggested to obtain a better integrated pH sensing property. Furthermore, a potential compensation method with a specially designed probe structure was proposed to correct possible errors caused by the potential drift of IrOx pH electrode in long-term pH monitoring. (c) The Author(s) 2017. Published by ECS. All rights reserved.