Abstract
Iridium oxide pH electrodes employing the carbonate melt oxidation method were fabricated with oxidation temperatures of 750 °C, 800 °C and 850 °C, respectively. Scanning electron microscope (SEM) and atomic force microscope (AFM) images showed that the oxide film regularized with the increase in oxidation temperatures. The pH response, response time and long-term stability of the electrodes indicated that the electrodes made at 850 °C had the best performance. X-ray photoelectron spectra (XPS) surveys investigated the change in the electrodes’ chemical composition and element oxidation states at 850 °C, and the results showed that the relative content of Ir3+ had increased by 23.9%, and the Ir4+ and Ir6+ had decreased by 10.9% and 13%, respectively, in the surface oxide layer after one month of aging. However, the relative contents of Ir3+, Ir4+ and Ir6+ were almost constant for the inner oxide layer. Meanwhile, the XPS result also indicated that the outer oxide layer of the electrode had a higher hydration degree than the inner oxide layer.
Highlights
PH is one of the most important parameters which has to be measured in many works of analytical chemistry research
The films appear different from the iridium oxide films made by the thermal
The surface morphology of the IrOX electrodes fabricated at different oxidation temperatures are at 750 ◦ C showed cracks particle and oxide distribution
Summary
PH is one of the most important parameters which has to be measured in many works of analytical chemistry research. Problems pertaining to electrode potential drift and lack of long-term stability remains, even when using the carbonate melt oxidation method to prepare IrOX electrodes [29,30,31]. O’Malley et al [31] have developed the vertical melt oxidation method which provides a more uniform reaction environment than previous methods They have investigated the effect of oxidation time on IrOX electrodes. Prior research has shown that the oxidation temperature, molten carbonate composition, oxidation time and hydration degree can influence the characteristics of IrOX electrodes. The carbonate melt oxidation method was adopted to fabricate IrOX electrodes, and three different oxidation temperatures (750 ◦ C, 800 ◦ C, 850 ◦ C) were chosen to complete the fabrication. Results will be helpful for preparation of solid pH sensor for in-situ pH measurements of hardened concrete
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